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  • Lunar and Planetary Science and Exploration  (127)
  • ASTROPHYSICS
  • EARTH RESOURCES AND REMOTE SENSING
  • INSTRUMENTATION AND PHOTOGRAPHY
  • Life and Medical Sciences
  • Models, Molecular
  • 2010-2014  (179)
  • 2012  (179)
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  • 2010-2014  (179)
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  • 1
    Publication Date: 2012-12-01
    Description: The Trypanosoma brucei cysteine protease cathepsin B (TbCatB), which is involved in host protein degradation, is a promising target to develop new treatments against sleeping sickness, a fatal disease caused by this protozoan parasite. The structure of the mature, active form of TbCatB has so far not provided sufficient information for the design of a safe and specific drug against T. brucei. By combining two recent innovations, in vivo crystallization and serial femtosecond crystallography, we obtained the room-temperature 2.1 angstrom resolution structure of the fully glycosylated precursor complex of TbCatB. The structure reveals the mechanism of native TbCatB inhibition and demonstrates that new biomolecular information can be obtained by the "diffraction-before-destruction" approach of x-ray free-electron lasers from hundreds of thousands of individual microcrystals.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3786669/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3786669/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Redecke, Lars -- Nass, Karol -- DePonte, Daniel P -- White, Thomas A -- Rehders, Dirk -- Barty, Anton -- Stellato, Francesco -- Liang, Mengning -- Barends, Thomas R M -- Boutet, Sebastien -- Williams, Garth J -- Messerschmidt, Marc -- Seibert, M Marvin -- Aquila, Andrew -- Arnlund, David -- Bajt, Sasa -- Barth, Torsten -- Bogan, Michael J -- Caleman, Carl -- Chao, Tzu-Chiao -- Doak, R Bruce -- Fleckenstein, Holger -- Frank, Matthias -- Fromme, Raimund -- Galli, Lorenzo -- Grotjohann, Ingo -- Hunter, Mark S -- Johansson, Linda C -- Kassemeyer, Stephan -- Katona, Gergely -- Kirian, Richard A -- Koopmann, Rudolf -- Kupitz, Chris -- Lomb, Lukas -- Martin, Andrew V -- Mogk, Stefan -- Neutze, Richard -- Shoeman, Robert L -- Steinbrener, Jan -- Timneanu, Nicusor -- Wang, Dingjie -- Weierstall, Uwe -- Zatsepin, Nadia A -- Spence, John C H -- Fromme, Petra -- Schlichting, Ilme -- Duszenko, Michael -- Betzel, Christian -- Chapman, Henry N -- 1R01GM095583/GM/NIGMS NIH HHS/ -- R01 GM095583/GM/NIGMS NIH HHS/ -- U54 GM094599/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2013 Jan 11;339(6116):227-30. doi: 10.1126/science.1229663. Epub 2012 Nov 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Joint Laboratory for Structural Biology of Infection and Inflammation, Institute of Biochemistry and Molecular Biology, University of Hamburg, and Institute of Biochemistry, University of Lubeck, at Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23196907" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Catalytic Domain ; Cathepsin B/antagonists & inhibitors/*chemistry ; Crystallization ; Crystallography, X-Ray ; Enzyme Precursors/chemistry ; Glycosylation ; Models, Molecular ; Molecular Sequence Data ; Protein Conformation ; Protozoan Proteins/antagonists & inhibitors/*chemistry ; Sf9 Cells ; Spodoptera ; Trypanosoma brucei brucei/*enzymology ; X-Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-10-12
    Description: Antigen-presenting molecules, encoded by the major histocompatibility complex (MHC) and CD1 family, bind peptide- and lipid-based antigens, respectively, for recognition by T cells. Mucosal-associated invariant T (MAIT) cells are an abundant population of innate-like T cells in humans that are activated by an antigen(s) bound to the MHC class I-like molecule MR1. Although the identity of MR1-restricted antigen(s) is unknown, it is present in numerous bacteria and yeast. Here we show that the structure and chemistry within the antigen-binding cleft of MR1 is distinct from the MHC and CD1 families. MR1 is ideally suited to bind ligands originating from vitamin metabolites. The structure of MR1 in complex with 6-formyl pterin, a folic acid (vitamin B9) metabolite, shows the pterin ring sequestered within MR1. Furthermore, we characterize related MR1-restricted vitamin derivatives, originating from the bacterial riboflavin (vitamin B2) biosynthetic pathway, which specifically and potently activate MAIT cells. Accordingly, we show that metabolites of vitamin B represent a class of antigen that are presented by MR1 for MAIT-cell immunosurveillance. As many vitamin biosynthetic pathways are unique to bacteria and yeast, our data suggest that MAIT cells use these metabolites to detect microbial infection.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kjer-Nielsen, Lars -- Patel, Onisha -- Corbett, Alexandra J -- Le Nours, Jerome -- Meehan, Bronwyn -- Liu, Ligong -- Bhati, Mugdha -- Chen, Zhenjun -- Kostenko, Lyudmila -- Reantragoon, Rangsima -- Williamson, Nicholas A -- Purcell, Anthony W -- Dudek, Nadine L -- McConville, Malcolm J -- O'Hair, Richard A J -- Khairallah, George N -- Godfrey, Dale I -- Fairlie, David P -- Rossjohn, Jamie -- McCluskey, James -- England -- Nature. 2012 Nov 29;491(7426):717-23. doi: 10.1038/nature11605. Epub 2012 Oct 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23051753" target="_blank"〉PubMed〈/a〉
    Keywords: Antigen Presentation ; Bacterial Infections/immunology/microbiology ; Binding Sites ; Cell Line ; Crystallography, X-Ray ; Folic Acid/chemistry/immunology/*metabolism ; Histocompatibility Antigens/chemistry/immunology ; Histocompatibility Antigens Class I/*chemistry/*immunology/metabolism ; Humans ; Immunologic Surveillance/immunology ; Jurkat Cells ; Ligands ; Lymphocyte Activation ; Models, Molecular ; Protein Refolding/drug effects ; Pterins/*chemistry/*immunology/metabolism/pharmacology ; Salmonella/immunology/metabolism ; Salmonella Infections/immunology/microbiology ; Static Electricity ; T-Lymphocytes/*immunology ; beta 2-Microglobulin/immunology/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2012-08-24
    Description: Materials exhibiting a spontaneous electrical polarization that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack: in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known to show ferroelectric switching, all below 71 kelvin. Here we describe supramolecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tayi, Alok S -- Shveyd, Alexander K -- Sue, Andrew C-H -- Szarko, Jodi M -- Rolczynski, Brian S -- Cao, Dennis -- Kennedy, T Jackson -- Sarjeant, Amy A -- Stern, Charlotte L -- Paxton, Walter F -- Wu, Wei -- Dey, Sanjeev K -- Fahrenbach, Albert C -- Guest, Jeffrey R -- Mohseni, Hooman -- Chen, Lin X -- Wang, Kang L -- Stoddart, J Fraser -- Stupp, Samuel I -- England -- Nature. 2012 Aug 23;488(7412):485-9. doi: 10.1038/nature11395.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22914165" target="_blank"〉PubMed〈/a〉
    Keywords: Anisotropy ; Crystallization ; *Electricity ; Electron Transport ; *Electrons ; Hydrogen Bonding ; Iron/*chemistry ; Models, Molecular ; Molecular Conformation ; Organometallic Compounds/*chemistry ; Surface Properties ; *Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2012-07-24
    Description: Medulloblastomas are the most common malignant brain tumours in children. Identifying and understanding the genetic events that drive these tumours is critical for the development of more effective diagnostic, prognostic and therapeutic strategies. Recently, our group and others described distinct molecular subtypes of medulloblastoma on the basis of transcriptional and copy number profiles. Here we use whole-exome hybrid capture and deep sequencing to identify somatic mutations across the coding regions of 92 primary medulloblastoma/normal pairs. Overall, medulloblastomas have low mutation rates consistent with other paediatric tumours, with a median of 0.35 non-silent mutations per megabase. We identified twelve genes mutated at statistically significant frequencies, including previously known mutated genes in medulloblastoma such as CTNNB1, PTCH1, MLL2, SMARCA4 and TP53. Recurrent somatic mutations were newly identified in an RNA helicase gene, DDX3X, often concurrent with CTNNB1 mutations, and in the nuclear co-repressor (N-CoR) complex genes GPS2, BCOR and LDB1. We show that mutant DDX3X potentiates transactivation of a TCF promoter and enhances cell viability in combination with mutant, but not wild-type, beta-catenin. Together, our study reveals the alteration of WNT, hedgehog, histone methyltransferase and now N-CoR pathways across medulloblastomas and within specific subtypes of this disease, and nominates the RNA helicase DDX3X as a component of pathogenic beta-catenin signalling in medulloblastoma.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413789/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413789/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pugh, Trevor J -- Weeraratne, Shyamal Dilhan -- Archer, Tenley C -- Pomeranz Krummel, Daniel A -- Auclair, Daniel -- Bochicchio, James -- Carneiro, Mauricio O -- Carter, Scott L -- Cibulskis, Kristian -- Erlich, Rachel L -- Greulich, Heidi -- Lawrence, Michael S -- Lennon, Niall J -- McKenna, Aaron -- Meldrim, James -- Ramos, Alex H -- Ross, Michael G -- Russ, Carsten -- Shefler, Erica -- Sivachenko, Andrey -- Sogoloff, Brian -- Stojanov, Petar -- Tamayo, Pablo -- Mesirov, Jill P -- Amani, Vladimir -- Teider, Natalia -- Sengupta, Soma -- Francois, Jessica Pierre -- Northcott, Paul A -- Taylor, Michael D -- Yu, Furong -- Crabtree, Gerald R -- Kautzman, Amanda G -- Gabriel, Stacey B -- Getz, Gad -- Jager, Natalie -- Jones, David T W -- Lichter, Peter -- Pfister, Stefan M -- Roberts, Thomas M -- Meyerson, Matthew -- Pomeroy, Scott L -- Cho, Yoon-Jae -- CA050661/CA/NCI NIH HHS/ -- L40 NS063706/NS/NINDS NIH HHS/ -- P30 HD018655/HD/NICHD NIH HHS/ -- P30 HD18655/HD/NICHD NIH HHS/ -- R01 CA030002/CA/NCI NIH HHS/ -- R01 CA105607/CA/NCI NIH HHS/ -- R01 CA109467/CA/NCI NIH HHS/ -- R01 CA148699/CA/NCI NIH HHS/ -- R01 CA154480/CA/NCI NIH HHS/ -- R01 NS046789/NS/NINDS NIH HHS/ -- R01CA105607/CA/NCI NIH HHS/ -- R01CA109467/CA/NCI NIH HHS/ -- R01CA148699/CA/NCI NIH HHS/ -- R25 NS070682/NS/NINDS NIH HHS/ -- R25NS070682/NS/NINDS NIH HHS/ -- U54 HG003067/HG/NHGRI NIH HHS/ -- U54HG003067/HG/NHGRI NIH HHS/ -- Canadian Institutes of Health Research/Canada -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Aug 2;488(7409):106-10. doi: 10.1038/nature11329.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22820256" target="_blank"〉PubMed〈/a〉
    Keywords: Cerebellar Neoplasms/classification/*genetics ; Child ; DEAD-box RNA Helicases/chemistry/genetics/metabolism ; DNA Helicases/chemistry/genetics ; DNA-Binding Proteins/genetics ; Exome/*genetics ; Genome, Human/*genetics ; Hedgehog Proteins/metabolism ; Histone-Lysine N-Methyltransferase/genetics/metabolism ; Humans ; Intracellular Signaling Peptides and Proteins/genetics ; LIM Domain Proteins/genetics ; Medulloblastoma/classification/*genetics ; Models, Molecular ; Mutation/*genetics ; Neoplasm Proteins/genetics ; Nuclear Proteins/chemistry/genetics ; Promoter Regions, Genetic/genetics ; Protein Structure, Tertiary/genetics ; Proto-Oncogene Proteins/genetics ; Receptors, Cell Surface/genetics ; Repressor Proteins/genetics ; Signal Transduction ; TCF Transcription Factors/metabolism ; Transcription Factors/chemistry/genetics ; Tumor Suppressor Protein p53/genetics ; Wnt Proteins/metabolism ; beta Catenin/genetics/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2012-06-23
    Description: Human leukocyte antigens (HLAs) are highly polymorphic proteins that initiate immunity by presenting pathogen-derived peptides to T cells. HLA polymorphisms mostly map to the antigen-binding cleft, thereby diversifying the repertoire of self-derived and pathogen-derived peptide antigens selected by different HLA allotypes. A growing number of immunologically based drug reactions, including abacavir hypersensitivity syndrome (AHS) and carbamazepine-induced Stevens-Johnson syndrome (SJS), are associated with specific HLA alleles. However, little is known about the underlying mechanisms of these associations, including AHS, a prototypical HLA-associated drug reaction occurring exclusively in individuals with the common histocompatibility allele HLA-B*57:01, and with a relative risk of more than 1,000 (refs 6, 7). We show that unmodified abacavir binds non-covalently to HLA-B*57:01, lying across the bottom of the antigen-binding cleft and reaching into the F-pocket, where a carboxy-terminal tryptophan typically anchors peptides bound to HLA-B*57:01. Abacavir binds with exquisite specificity to HLA-B*57:01, changing the shape and chemistry of the antigen-binding cleft, thereby altering the repertoire of endogenous peptides that can bind HLA-B*57:01. In this way, abacavir guides the selection of new endogenous peptides, inducing a marked alteration in 'immunological self'. The resultant peptide-centric 'altered self' activates abacavir-specific T-cells, thereby driving polyclonal CD8 T-cell activation and a systemic reaction manifesting as AHS. We also show that carbamazepine, a widely used anti-epileptic drug associated with hypersensitivity reactions in HLA-B*15:02 individuals, binds to this allotype, producing alterations in the repertoire of presented self peptides. Our findings simultaneously highlight the importance of HLA polymorphism in the evolution of pharmacogenomics and provide a general mechanism for some of the growing number of HLA-linked hypersensitivities that involve small-molecule drugs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Illing, Patricia T -- Vivian, Julian P -- Dudek, Nadine L -- Kostenko, Lyudmila -- Chen, Zhenjun -- Bharadwaj, Mandvi -- Miles, John J -- Kjer-Nielsen, Lars -- Gras, Stephanie -- Williamson, Nicholas A -- Burrows, Scott R -- Purcell, Anthony W -- Rossjohn, Jamie -- McCluskey, James -- England -- Nature. 2012 Jun 28;486(7404):554-8. doi: 10.1038/nature11147.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722860" target="_blank"〉PubMed〈/a〉
    Keywords: Antigen Presentation/*drug effects ; Autoimmunity/*drug effects/*immunology ; Binding Sites ; Blood Donors ; CD8-Positive T-Lymphocytes/drug effects/immunology ; Carbamazepine/pharmacology ; Dideoxynucleosides/*pharmacology ; Drug Hypersensitivity ; HLA-B Antigens/chemistry/*immunology ; Humans ; Models, Molecular ; Protein Conformation ; Syndrome ; T-Lymphocytes/*drug effects/*immunology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2012-08-14
    Description: Cornelia de Lange syndrome (CdLS) is a dominantly inherited congenital malformation disorder, caused by mutations in the cohesin-loading protein NIPBL for nearly 60% of individuals with classical CdLS, and by mutations in the core cohesin components SMC1A (~5%) and SMC3 (〈1%) for a smaller fraction of probands. In humans, the multisubunit complex cohesin is made up of SMC1, SMC3, RAD21 and a STAG protein. These form a ring structure that is proposed to encircle sister chromatids to mediate sister chromatid cohesion and also has key roles in gene regulation. SMC3 is acetylated during S-phase to establish cohesiveness of chromatin-loaded cohesin, and in yeast, the class I histone deacetylase Hos1 deacetylates SMC3 during anaphase. Here we identify HDAC8 as the vertebrate SMC3 deacetylase, as well as loss-of-function HDAC8 mutations in six CdLS probands. Loss of HDAC8 activity results in increased SMC3 acetylation and inefficient dissolution of the 'used' cohesin complex released from chromatin in both prophase and anaphase. SMC3 with retained acetylation is loaded onto chromatin, and chromatin immunoprecipitation sequencing analysis demonstrates decreased occupancy of cohesin localization sites that results in a consistent pattern of altered transcription seen in CdLS cell lines with either NIPBL or HDAC8 mutations.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443318/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443318/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Deardorff, Matthew A -- Bando, Masashige -- Nakato, Ryuichiro -- Watrin, Erwan -- Itoh, Takehiko -- Minamino, Masashi -- Saitoh, Katsuya -- Komata, Makiko -- Katou, Yuki -- Clark, Dinah -- Cole, Kathryn E -- De Baere, Elfride -- Decroos, Christophe -- Di Donato, Nataliya -- Ernst, Sarah -- Francey, Lauren J -- Gyftodimou, Yolanda -- Hirashima, Kyotaro -- Hullings, Melanie -- Ishikawa, Yuuichi -- Jaulin, Christian -- Kaur, Maninder -- Kiyono, Tohru -- Lombardi, Patrick M -- Magnaghi-Jaulin, Laura -- Mortier, Geert R -- Nozaki, Naohito -- Petersen, Michael B -- Seimiya, Hiroyuki -- Siu, Victoria M -- Suzuki, Yutaka -- Takagaki, Kentaro -- Wilde, Jonathan J -- Willems, Patrick J -- Prigent, Claude -- Gillessen-Kaesbach, Gabriele -- Christianson, David W -- Kaiser, Frank J -- Jackson, Laird G -- Hirota, Toru -- Krantz, Ian D -- Shirahige, Katsuhiko -- GM49758/GM/NIGMS NIH HHS/ -- K08 HD055488/HD/NICHD NIH HHS/ -- K08HD055488/HD/NICHD NIH HHS/ -- P01 HD052860/HD/NICHD NIH HHS/ -- R01 GM049758/GM/NIGMS NIH HHS/ -- England -- Nature. 2012 Sep 13;489(7415):313-7. doi: 10.1038/nature11316.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Human Genetics and Molecular Biology, The Children's Hospital of Philadelphia, Pennsylvania 19104, USA. deardorff@email.chop.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22885700" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylation ; Adaptor Proteins, Signal Transducing/metabolism ; Anaphase ; Binding Sites ; Cell Cycle Proteins/chemistry/*metabolism ; Chondroitin Sulfate Proteoglycans/chemistry/metabolism ; Chromatin/genetics/metabolism ; Chromatin Immunoprecipitation ; Chromosomal Proteins, Non-Histone/chemistry/*metabolism ; Crystallography, X-Ray ; De Lange Syndrome/*genetics/*metabolism ; Female ; Fibroblasts ; HeLa Cells ; Histone Deacetylases/chemistry/deficiency/*genetics/metabolism ; Humans ; Male ; Models, Molecular ; Mutant Proteins/chemistry/genetics/metabolism ; Mutation/*genetics ; Nuclear Proteins/metabolism ; Phosphoproteins/metabolism ; Prophase ; Protein Conformation ; Proteins/genetics ; Repressor Proteins/chemistry/deficiency/*genetics/metabolism ; Transcription, Genetic
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2019-07-19
    Description: Comets retain relatively primitive icy material remaining from the epoch of Solar System formation, however the extent to which they are modified from their initial state remains a key question in cometary science. High-resolution lR spectroscopy has emerged as a powerful tool for measuring vibrational emissions from primary volatiles (i.e., those contained in the nuclei of comets). With modern instrumentation, most notably NIRSPEC at the Keck II 10-m telescope, we can quantify species of astrobiological importance (e.g., H20, C2H2, CH4, C2H6, CO, H2CO, CH30H, HCN, NH3). In space environments, compounds of keen interest to astrobiology could originate from HCN and NH3 (leading to amino acids), H2CO (leading to sugars), or C2H6 and CH4 (suggested precursors of ethyl- and methylamine). Measuring the abundances of these precursor molecules (and their variability among comets) is a feasible task that contributes to understanding their delivery to Earth's early biosphere and to the synthesis of more complex pre biotic compounds. Over 20 comets have now been measured with IR spectroscopy, and this sample reveals significant diversity in primary volatile compositions. From this, a taxonomic classification scheme is emerging, presumably reflecting the diverse conditions experienced by pre-cometary grains in interstellar and subsequent nebular environs. The importance of H-atom addition to C2H2 on the surfaces of interstellar grains to produce C2H6 was validated by the discovery of abundant ethane in comet C/1996 B2 (Hyakutake) with C2H6/CH4 well above that achievable by gas-phase chemistry , and then in irradiation experiments on laboratory ices at 10 - 50 K. The large abundance ratios C2H6/CH4 observed universally in comets establish H-atom addition as an important and likely ubiquitous process, and comparing C2H6/C2H2 among comets can provide information on its efficiency. The IR is uniquely capable since symmetric hydrocarbons (e.g., C2H2, CH4, C2H6) have no electric dipole moment and thus no allowed pure rotational transitions. CO should also be hydrogenated on grain surfaces. Irradiation experiments on interstellar ice analogs show this to require very low temperatures, the resulting yields of H2CO and CH30H being highly dependent on temperature in the range approx 10 - 25 K. The relative abundances of these chemically-related molecules in comets provide one measure of the efficiency of H-atom addition to CO Oxidation of CO is also important on grain mantles, as evidenced by the widespread presence of C02 ice towards interstellar sources observed with ISO and in a survey of 17 comets observed with AKARI. H-atom addition to C2H2 produces the vinyl radical, and through subsequent oxidation1reduction reactions can lead to vinyl alcohol, acetaldehyde, and ethanol This may have implications for interpreting observed abundance ratios CO/C2H2. We will discuss possible implications regarding formation conditions in the context of measured primary volatile compositions, emphasizing recently observed comets and published results. These are continually providing new insights regarding our taxonomic scheme and also delivery of pre-biological material to the young Earth.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC.ABS.00317.2012 , Astrobiology Science Conference 2012; Apr 16, 2012 - Apr 20, 2012; Atlanta, GA; United States
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  • 8
    Publication Date: 2012-03-16
    Description: Derivatives of vitamin B(12) are used in methyl group transfer in biological processes as diverse as methionine synthesis in humans and CO(2) fixation in acetogenic bacteria. This seemingly straightforward reaction requires large, multimodular enzyme complexes that adopt multiple conformations to alternately activate, protect and perform catalysis on the reactive B(12) cofactor. Crystal structures determined thus far have provided structural information for only fragments of these complexes, inspiring speculation about the overall protein assembly and conformational movements inherent to activity. Here we present X-ray crystal structures of a complete 220 kDa complex that contains all enzymes responsible for B(12)-dependent methyl transfer, namely the corrinoid iron-sulphur protein and its methyltransferase from the model acetogen Moorella thermoacetica. These structures provide the first three-dimensional depiction of all protein modules required for the activation, protection and catalytic steps of B(12)-dependent methyl transfer. In addition, the structures capture B(12) at multiple locations between its 'resting' and catalytic positions, allowing visualization of the dramatic protein rearrangements that enable methyl transfer and identification of the trajectory for B(12) movement within the large enzyme scaffold. The structures are also presented alongside in crystallo spectroscopic data, which confirm enzymatic activity within crystals and demonstrate the largest known conformational movements of proteins in a crystalline state. Taken together, this work provides a model for the molecular juggling that accompanies turnover and helps explain why such an elaborate protein framework is required for such a simple, yet biologically essential reaction.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326194/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326194/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kung, Yan -- Ando, Nozomi -- Doukov, Tzanko I -- Blasiak, Leah C -- Bender, Gunes -- Seravalli, Javier -- Ragsdale, Stephen W -- Drennan, Catherine L -- GM39451/GM/NIGMS NIH HHS/ -- GM69857/GM/NIGMS NIH HHS/ -- R01 GM039451/GM/NIGMS NIH HHS/ -- R01 GM039451-25/GM/NIGMS NIH HHS/ -- R01 GM069857/GM/NIGMS NIH HHS/ -- R37 GM039451/GM/NIGMS NIH HHS/ -- RR-15301/RR/NCRR NIH HHS/ -- T32 GM008334/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Mar 14;484(7393):265-9. doi: 10.1038/nature10916.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22419154" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Biocatalysis ; Corrinoids/metabolism ; Crystallography, X-Ray ; Folic Acid/metabolism ; Iron-Sulfur Proteins/*chemistry/*metabolism ; Methylation ; Methyltransferases/*chemistry/*metabolism ; Models, Biological ; Models, Molecular ; Moorella/chemistry/*enzymology ; Protein Multimerization ; Protein Structure, Tertiary ; Vitamin B 12/*metabolism
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 2012-10-23
    Description: Calcium ions (Ca(2+)) have an important role as secondary messengers in numerous signal transduction processes, and cells invest much energy in controlling and maintaining a steep gradient between intracellular ( approximately 0.1-micromolar) and extracellular ( approximately 2-millimolar) Ca(2+) concentrations. Calmodulin-stimulated calcium pumps, which include the plasma-membrane Ca(2+)-ATPases (PMCAs), are key regulators of intracellular Ca(2+) in eukaryotes. They contain a unique amino- or carboxy-terminal regulatory domain responsible for autoinhibition, and binding of calcium-loaded calmodulin to this domain releases autoinhibition and activates the pump. However, the structural basis for the activation mechanism is unknown and a key remaining question is how calmodulin-mediated PMCA regulation can cover both basal Ca(2+) levels in the nanomolar range as well as micromolar-range Ca(2+) transients generated by cell stimulation. Here we present an integrated study combining the determination of the high-resolution crystal structure of a PMCA regulatory-domain/calmodulin complex with in vivo characterization and biochemical, biophysical and bioinformatics data that provide mechanistic insights into a two-step PMCA activation mechanism mediated by calcium-loaded calmodulin. The structure shows the entire PMCA regulatory domain and reveals an unexpected 2:1 stoichiometry with two calcium-loaded calmodulin molecules binding to different sites on a long helix. A multifaceted characterization of the role of both sites leads to a general structural model for calmodulin-mediated regulation of PMCAs that allows stringent, highly responsive control of intracellular calcium in eukaryotes, making it possible to maintain a stable, basal level at a threshold Ca(2+) concentration, where steep activation occurs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tidow, Henning -- Poulsen, Lisbeth R -- Andreeva, Antonina -- Knudsen, Michael -- Hein, Kim L -- Wiuf, Carsten -- Palmgren, Michael G -- Nissen, Poul -- MC_U105192716/Medical Research Council/United Kingdom -- England -- Nature. 2012 Nov 15;491(7424):468-72. doi: 10.1038/nature11539. Epub 2012 Oct 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23086147" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arabidopsis/chemistry/enzymology/*metabolism ; Arabidopsis Proteins/*chemistry/genetics/*metabolism ; Binding Sites ; Calcium/*metabolism ; Calcium-Transporting ATPases/*chemistry/genetics/*metabolism ; Calmodulin/*chemistry/metabolism ; Enzyme Activation ; Eukaryota/*metabolism ; Intracellular Space/chemistry/metabolism ; Models, Molecular ; Molecular Sequence Data ; Protein Binding ; Protein Structure, Tertiary ; Sequence Alignment
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2012-10-02
    Description: The genome-wide identification of pairs of interacting proteins is an important step in the elucidation of cell regulatory mechanisms. Much of our present knowledge derives from high-throughput techniques such as the yeast two-hybrid assay and affinity purification, as well as from manual curation of experiments on individual systems. A variety of computational approaches based, for example, on sequence homology, gene co-expression and phylogenetic profiles, have also been developed for the genome-wide inference of protein-protein interactions (PPIs). Yet comparative studies suggest that the development of accurate and complete repertoires of PPIs is still in its early stages. Here we show that three-dimensional structural information can be used to predict PPIs with an accuracy and coverage that are superior to predictions based on non-structural evidence. Moreover, an algorithm, termed PrePPI, which combines structural information with other functional clues, is comparable in accuracy to high-throughput experiments, yielding over 30,000 high-confidence interactions for yeast and over 300,000 for human. Experimental tests of a number of predictions demonstrate the ability of the PrePPI algorithm to identify unexpected PPIs of considerable biological interest. The surprising effectiveness of three-dimensional structural information can be attributed to the use of homology models combined with the exploitation of both close and remote geometric relationships between proteins.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3482288/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3482288/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Qiangfeng Cliff -- Petrey, Donald -- Deng, Lei -- Qiang, Li -- Shi, Yu -- Thu, Chan Aye -- Bisikirska, Brygida -- Lefebvre, Celine -- Accili, Domenico -- Hunter, Tony -- Maniatis, Tom -- Califano, Andrea -- Honig, Barry -- CA082683/CA/NCI NIH HHS/ -- CA121852/CA/NCI NIH HHS/ -- DK057539/DK/NIDDK NIH HHS/ -- GM030518/GM/NIGMS NIH HHS/ -- GM094597/GM/NIGMS NIH HHS/ -- R01 CA082683/CA/NCI NIH HHS/ -- R01 DK057539/DK/NIDDK NIH HHS/ -- R01 GM030518/GM/NIGMS NIH HHS/ -- R01 NS043915/NS/NINDS NIH HHS/ -- R01NS043915/NS/NINDS NIH HHS/ -- U54 CA121852/CA/NCI NIH HHS/ -- U54 GM094597/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Oct 25;490(7421):556-60. doi: 10.1038/nature11503. Epub 2012 Sep 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Columbia University, New York, New York 10032, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23023127" target="_blank"〉PubMed〈/a〉
    Keywords: *Algorithms ; Animals ; Bayes Theorem ; Brain/metabolism ; Cadherins/metabolism ; High-Throughput Screening Assays ; Humans ; Matrix Attachment Region Binding Proteins/metabolism ; Mice ; Models, Molecular ; PPAR gamma/metabolism ; Phylogeny ; Protein Binding ; Protein Conformation ; Protein Interaction Mapping/*methods ; *Protein Interaction Maps ; Protein Kinases/chemistry/metabolism ; Proteins/*chemistry/*metabolism ; Proteome/chemistry/metabolism ; Proteomics/*methods ; ROC Curve ; Reproducibility of Results ; Saccharomyces cerevisiae/chemistry/metabolism ; Suppressor of Cytokine Signaling Proteins/metabolism ; Transcription Factors/metabolism
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    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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