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  • Amidohydrolases/*chemistry/deficiency/genetics/*metabolism  (1)
  • Extraterrestrial Environment  (1)
  • 2005-2009  (2)
  • 1
    Publication Date: 2008-02-22
    Description: Messenger-RNA-directed protein synthesis is accomplished by the ribosome. In eubacteria, this complex process is initiated by a specialized transfer RNA charged with formylmethionine (tRNA(fMet)). The amino-terminal formylated methionine of all bacterial nascent polypeptides blocks the reactive amino group to prevent unfavourable side-reactions and to enhance the efficiency of translation initiation. The first enzymatic factor that processes nascent chains is peptide deformylase (PDF); it removes this formyl group as polypeptides emerge from the ribosomal tunnel and before the newly synthesized proteins can adopt their native fold, which may bury the N terminus. Next, the N-terminal methionine is excised by methionine aminopeptidase. Bacterial PDFs are metalloproteases sharing a conserved N-terminal catalytic domain. All Gram-negative bacteria, including Escherichia coli, possess class-1 PDFs characterized by a carboxy-terminal alpha-helical extension. Studies focusing on PDF as a target for antibacterial drugs have not revealed the mechanism of its co-translational mode of action despite indications in early work that it co-purifies with ribosomes. Here we provide biochemical evidence that E. coli PDF interacts directly with the ribosome via its C-terminal extension. Crystallographic analysis of the complex between the ribosome-interacting helix of PDF and the ribosome at 3.7 A resolution reveals that the enzyme orients its active site towards the ribosomal tunnel exit for efficient co-translational processing of emerging nascent chains. Furthermore, we have found that the interaction of PDF with the ribosome enhances cell viability. These results provide the structural basis for understanding the coupling between protein synthesis and enzymatic processing of nascent chains, and offer insights into the interplay of PDF with the ribosome-associated chaperone trigger factor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bingel-Erlenmeyer, Rouven -- Kohler, Rebecca -- Kramer, Gunter -- Sandikci, Arzu -- Antolic, Snjezana -- Maier, Timm -- Schaffitzel, Christiane -- Wiedmann, Brigitte -- Bukau, Bernd -- Ban, Nenad -- England -- Nature. 2008 Mar 6;452(7183):108-11. doi: 10.1038/nature06683. Epub 2008 Feb 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18288106" target="_blank"〉PubMed〈/a〉
    Keywords: Amidohydrolases/*chemistry/deficiency/genetics/*metabolism ; Amino Acid Sequence ; Arabinose/metabolism ; Binding Sites ; Crystallography, X-Ray ; Escherichia coli/*enzymology/genetics/growth & development/metabolism ; Genetic Complementation Test ; Models, Biological ; Models, Molecular ; Molecular Sequence Data ; N-Formylmethionine/metabolism ; Peptidylprolyl Isomerase/metabolism ; Protein Binding ; *Protein Biosynthesis ; *Protein Processing, Post-Translational ; Protein Structure, Secondary ; RNA, Transfer, Met/genetics/metabolism ; Ribosome Subunits/chemistry/metabolism ; Ribosomes/*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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  • 2
    Publication Date: 2009-09-26
    Description: The search for water on the surface of the anhydrous Moon had remained an unfulfilled quest for 40 years. However, the Moon Mineralogy Mapper (M3) on Chandrayaan-1 has recently detected absorption features near 2.8 to 3.0 micrometers on the surface of the Moon. For silicate bodies, such features are typically attributed to hydroxyl- and/or water-bearing materials. On the Moon, the feature is seen as a widely distributed absorption that appears strongest at cooler high latitudes and at several fresh feldspathic craters. The general lack of correlation of this feature in sunlit M3 data with neutron spectrometer hydrogen abundance data suggests that the formation and retention of hydroxyl and water are ongoing surficial processes. Hydroxyl/water production processes may feed polar cold traps and make the lunar regolith a candidate source of volatiles for human exploration.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pieters, C M -- Goswami, J N -- Clark, R N -- Annadurai, M -- Boardman, J -- Buratti, B -- Combe, J-P -- Dyar, M D -- Green, R -- Head, J W -- Hibbitts, C -- Hicks, M -- Isaacson, P -- Klima, R -- Kramer, G -- Kumar, S -- Livo, E -- Lundeen, S -- Malaret, E -- McCord, T -- Mustard, J -- Nettles, J -- Petro, N -- Runyon, C -- Staid, M -- Sunshine, J -- Taylor, L A -- Tompkins, S -- Varanasi, P -- New York, N.Y. -- Science. 2009 Oct 23;326(5952):568-72. doi: 10.1126/science.1178658. Epub 2009 Sep 24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Brown University, Providence, RI 02912, USA. carle_pieters@brown.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19779151" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; *Hydroxyl Radical ; Minerals ; *Moon ; Spacecraft ; Spectrum Analysis ; Sunlight ; Temperature ; *Water
    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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