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  • 1
    Publication Date: 2011-06-15
    Description: Malaria parasite cell motility is a process that is dependent on the dynamic turnover of parasite-derived actin filaments. Despite its central role, actin's polymerization state is controlled by a set of identifiable regulators that is markedly reduced compared with those of other eukaryotic cells. In Plasmodium falciparum, the most virulent species that affects humans, this minimal repertoire includes two members of the actin-depolymerizing factor/cofilin (AC) family of proteins, P. falciparum actin-depolymerizing factor 1 (PfADF1) and P. falciparum actin-depolymerizing factor 2. This essential class of actin regulator is involved in the control of filament dynamics at multiple levels, from monomer binding through to filament depolymerization and severing. Previous biochemical analyses have suggested that PfADF1 sequesters monomeric actin but, unlike most eukaryotic counterparts, has limited potential to bind or depolymerize filaments. The molecular basis for these unusual properties and implications for parasite cell motility have not been established. Here we present the crystal structure of an apicomplexan AC protein, PfADF1. We show that PfADF1 lacks critical residues previously implicated as essential for AC-mediated actin filament binding and disassembly, having a substantially reduced filament-binding loop and C-terminal α4 helix. Despite this divergence in structure, we demonstrate that PfADF1 is capable of efficient actin filament severing. Furthermore, this severing occurs despite PfADF1’s low binding affinity for filaments. Comparative structural analysis along with biochemical and microscopy evidence establishes that severing is reliant on the availability of an exposed basic residue in the filament-binding loop, a conserved minimal requirement that defines AC-mediated filament disassembly across eukaryotic cells.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 2
    Publication Date: 2014-12-04
    Description: Ryanodine receptors (RyRs) mediate the rapid release of calcium (Ca(2+)) from intracellular stores into the cytosol, which is essential for numerous cellular functions including excitation-contraction coupling in muscle. Lack of sufficient structural detail has impeded understanding of RyR gating and regulation. Here we report the closed-state structure of the 2.3-megadalton complex of the rabbit skeletal muscle type 1 RyR (RyR1), solved by single-particle electron cryomicroscopy at an overall resolution of 4.8 A. We fitted a polyalanine-level model to all 3,757 ordered residues in each protomer, defining the transmembrane pore in unprecedented detail and placing all cytosolic domains as tertiary folds. The cytosolic assembly is built on an extended alpha-solenoid scaffold connecting key regulatory domains to the pore. The RyR1 pore architecture places it in the six-transmembrane ion channel superfamily. A unique domain inserted between the second and third transmembrane helices interacts intimately with paired EF-hands originating from the alpha-solenoid scaffold, suggesting a mechanism for channel gating by Ca(2+).〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4300236/" 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/PMC4300236/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zalk, Ran -- Clarke, Oliver B -- des Georges, Amedee -- Grassucci, Robert A -- Reiken, Steven -- Mancia, Filippo -- Hendrickson, Wayne A -- Frank, Joachim -- Marks, Andrew R -- P01 HL081172/HL/NHLBI NIH HHS/ -- R01 AR060037/AR/NIAMS NIH HHS/ -- R01 GM029169/GM/NIGMS NIH HHS/ -- R01 HL061503/HL/NHLBI NIH HHS/ -- R01 HL083418/HL/NHLBI NIH HHS/ -- R01AR060037/AR/NIAMS NIH HHS/ -- R01GM29169/GM/NIGMS NIH HHS/ -- R01HL061503/HL/NHLBI NIH HHS/ -- U54GM095315/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Jan 1;517(7532):44-9. doi: 10.1038/nature13950. Epub 2014 Dec 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA. ; Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA. ; 1] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA [2] Howard Hughes Medical Institute, Columbia University, New York, New York 10032, USA. ; 1] Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA [2] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA. ; 1] Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA [2] Howard Hughes Medical Institute, Columbia University, New York, New York 10032, USA [3] Department of Biological Sciences, Columbia University, New York, New York 10027, USA. ; 1] Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA [2] Department of Medicine, Columbia University, New York, New York 10032, USA [3] Wu Center for Molecular Cardiology, College of Physicians and Surgeons of 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/25470061" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/deficiency/metabolism/pharmacology ; Cell Membrane/metabolism ; Cryoelectron Microscopy ; Cytosol/metabolism ; Ion Channel Gating/drug effects ; Muscle, Skeletal/chemistry ; Protein Structure, Tertiary ; Rabbits ; Ryanodine Receptor Calcium Release Channel/*chemistry/metabolism/*ultrastructure ; Tacrolimus Binding Proteins/chemistry/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: 2016-02-26
    Description: Polymyxins are antibiotics used in the last line of defense to combat multidrug-resistant infections by Gram-negative bacteria. Polymyxin resistance arises through charge modification of the bacterial outer membrane with the attachment of the cationic sugar 4-amino-4-deoxy-l-arabinose to lipid A, a reaction catalyzed by the integral membrane lipid-to-lipid glycosyltransferase 4-amino-4-deoxy-L-arabinose transferase (ArnT). Here, we report crystal structures of ArnT from Cupriavidus metallidurans, alone and in complex with the lipid carrier undecaprenyl phosphate, at 2.8 and 3.2 angstrom resolution, respectively. The structures show cavities for both lipidic substrates, which converge at the active site. A structural rearrangement occurs on undecaprenyl phosphate binding, which stabilizes the active site and likely allows lipid A binding. Functional mutagenesis experiments based on these structures suggest a mechanistic model for ArnT family enzymes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petrou, Vasileios I -- Herrera, Carmen M -- Schultz, Kathryn M -- Clarke, Oliver B -- Vendome, Jeremie -- Tomasek, David -- Banerjee, Surajit -- Rajashankar, Kanagalaghatta R -- Belcher Dufrisne, Meagan -- Kloss, Brian -- Kloppmann, Edda -- Rost, Burkhard -- Klug, Candice S -- Trent, M Stephen -- Shapiro, Lawrence -- Mancia, Filippo -- AI064184/AI/NIAID NIH HHS/ -- AI076322/AI/NIAID NIH HHS/ -- P41 GM103403/GM/NIGMS NIH HHS/ -- R01 GM111980/GM/NIGMS NIH HHS/ -- S10 RR029205/RR/NCRR NIH HHS/ -- U54 GM095315/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2016 Feb 5;351(6273):608-12. doi: 10.1126/science.aad1172.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA. ; Department of Infectious Diseases, University of Georgia, College of Veterinary Medicine, Athens, GA 30602, USA. ; Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA. ; Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. ; Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. Department of Systems Biology, Columbia University, New York, NY 10032, USA. ; Department of Chemistry and Chemical Biology, Cornell University, Northeastern Collaborative Access Team, Advanced Photon Source, Argonne, IL 60439, USA. ; New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. ; Department of Informatics, Bioinformatics and Computational Biology, Technische Universitat Munchen, Boltzmannstrasse 3, 85748 Garching, Germany. ; Department of Informatics, Bioinformatics and Computational Biology, Technische Universitat Munchen, Boltzmannstrasse 3, 85748 Garching, Germany. Institute for Advanced Study (TUM-IAS), Technische Universitat Munchen, Boltzmannstrasse 3, 85748 Garching, Germany. ; Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA. fm123@cumc.columbia.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26912703" target="_blank"〉PubMed〈/a〉
    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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  • 4
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  • 6
    Publication Date: 2011-04-27
    Description: Schistosomiasis is an infectious disease caused by parasites of the phylum platyhelminthe. Here, we describe the identification and characterization of a Bcl-2–regulated apoptosis pathway in Schistosoma japonicum and S. mansoni. Genomic, biochemical, and cell-based mechanistic studies provide evidence for a tripartite pathway, similar to that in humans including BH3-only proteins that are inhibited by prosurvival Bcl-2–like molecules, and Bax/Bak-like proteins that facilitate mitochondrial outer-membrane permeabilization. Because Bcl-2 proteins have been successfully targeted with “BH3 mimetic” drugs, particularly in the treatment of cancer, we investigated whether schistosome apoptosis pathways could provide targets for future antischistosomal drug discovery efforts. Accordingly, we showed that a schistosome prosurvival protein, sjA, binds ABT-737, a well-characterized BH3 mimetic. A crystal structure of sjA bound to a BH3 peptide provides direct evidence for the feasibility of developing BH3 mimetics to target Bcl-2 prosurvival proteins in schistosomes, suggesting an alternative application for this class of drugs beyond cancer treatment.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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