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  • Substrate Specificity  (2)
  • 2005-2009  (2)
  • 1920-1924
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  • 2005-2009  (2)
  • 1920-1924
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  • 1
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    Structural basis for translational fidelity ensured by transfer RNA lysidine synthetase (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-10-23
    Description: Maturation of precursor transfer RNA (pre-tRNA) includes excision of the 5' leader and 3' trailer sequences, removal of introns and addition of the CCA terminus. Nucleotide modifications are incorporated at different stages of tRNA processing, after the RNA molecule adopts the proper conformation. In bacteria, tRNA(Ile2) lysidine synthetase (TilS) modifies cytidine into lysidine (L; 2-lysyl-cytidine) at the first anticodon of tRNA(Ile2) (refs 4-9). This modification switches tRNA(Ile2) from a methionine-specific to an isoleucine-specific tRNA. However, the aminoacylation of tRNA(Ile2) by methionyl-tRNA synthetase (MetRS), before the modification by TilS, might lead to the misincorporation of methionine in response to isoleucine codons. The mechanism used by bacteria to avoid this pitfall is unknown. Here we show that the TilS enzyme specifically recognizes and modifies tRNA(Ile2) in its precursor form, thereby avoiding translation errors. We identified the lysidine modification in pre-tRNA(Ile2) isolated from RNase-E-deficient Escherichia coli and did not detect mature tRNA(Ile2) lacking this modification. Our kinetic analyses revealed that TilS can modify both types of RNA molecule with comparable efficiencies. X-ray crystallography and mutational analyses revealed that TilS specifically recognizes the entire L-shape structure in pre-tRNA(Ile2) through extensive interactions coupled with sequential domain movements. Our results demonstrate how TilS prevents the recognition of tRNA(Ile2) by MetRS and achieves high specificity for its substrate. These two key points form the basis for maintaining the fidelity of isoleucine codon translation in bacteria. Our findings also provide a rationale for the necessity of incorporating specific modifications at the precursor level during tRNA biogenesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nakanishi, Kotaro -- Bonnefond, Luc -- Kimura, Satoshi -- Suzuki, Tsutomu -- Ishitani, Ryuichiro -- Nureki, Osamu -- England -- Nature. 2009 Oct 22;461(7267):1144-8. doi: 10.1038/nature08474.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa 225-8501, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19847269" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acyl-tRNA Synthetases/*chemistry/genetics/*metabolism ; Apoproteins/genetics/metabolism ; Bacillus subtilis ; Bacterial Proteins/*chemistry/genetics/*metabolism ; Base Sequence ; Catalytic Domain ; Crystallography, X-Ray ; Escherichia coli ; Geobacillus ; Kinetics ; Lysine/analogs & derivatives/metabolism ; Mass Spectrometry ; Models, Molecular ; Molecular Sequence Data ; *Protein Biosynthesis ; Pyrimidine Nucleosides/metabolism ; RNA, Transfer, Ile/genetics/metabolism ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Uptake through glycoprotein 2 of FimH(+) bacteria by M cells initiates mucosal immune response (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-11-13
    Description: The mucosal immune system forms the largest part of the entire immune system, containing about three-quarters of all lymphocytes and producing grams of secretory IgA daily to protect the mucosal surface from pathogens. To evoke the mucosal immune response, antigens on the mucosal surface must be transported across the epithelial barrier into organized lymphoid structures such as Peyer's patches. This function, called antigen transcytosis, is mediated by specialized epithelial M cells. The molecular mechanisms promoting this antigen uptake, however, are largely unknown. Here we report that glycoprotein 2 (GP2), specifically expressed on the apical plasma membrane of M cells among enterocytes, serves as a transcytotic receptor for mucosal antigens. Recombinant GP2 protein selectively bound a subset of commensal and pathogenic enterobacteria, including Escherichia coli and Salmonella enterica serovar Typhimurium (S. Typhimurium), by recognizing FimH, a component of type I pili on the bacterial outer membrane. Consistently, these bacteria were colocalized with endogenous GP2 on the apical plasma membrane as well as in cytoplasmic vesicles in M cells. Moreover, deficiency of bacterial FimH or host GP2 led to defects in transcytosis of type-I-piliated bacteria through M cells, resulting in an attenuation of antigen-specific immune responses in Peyer's patches. GP2 is therefore a previously unrecognized transcytotic receptor on M cells for type-I-piliated bacteria and is a prerequisite for the mucosal immune response to these bacteria. Given that M cells are considered a promising target for oral vaccination against various infectious diseases, the GP2-dependent transcytotic pathway could provide a new target for the development of M-cell-targeted mucosal vaccines.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hase, Koji -- Kawano, Kazuya -- Nochi, Tomonori -- Pontes, Gemilson Soares -- Fukuda, Shinji -- Ebisawa, Masashi -- Kadokura, Kazunori -- Tobe, Toru -- Fujimura, Yumiko -- Kawano, Sayaka -- Yabashi, Atsuko -- Waguri, Satoshi -- Nakato, Gaku -- Kimura, Shunsuke -- Murakami, Takaya -- Iimura, Mitsutoshi -- Hamura, Kimiyo -- Fukuoka, Shin-Ichi -- Lowe, Anson W -- Itoh, Kikuji -- Kiyono, Hiroshi -- Ohno, Hiroshi -- DK43294/DK/NIDDK NIH HHS/ -- DK56339/DK/NIDDK NIH HHS/ -- England -- Nature. 2009 Nov 12;462(7270):226-30. doi: 10.1038/nature08529.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory for Epithelial Immunobiology, Research Center for Allergy and Immunology, RIKEN, Kanagawa 230-0045, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19907495" target="_blank"〉PubMed〈/a〉
    Keywords: Adhesins, Escherichia coli/genetics/immunology/*metabolism ; Animals ; Antigens, Bacterial/genetics/immunology/*metabolism ; Cell Line ; Epithelial Cells/*immunology/metabolism ; Escherichia coli/immunology/metabolism ; Fimbriae Proteins/genetics/immunology/*metabolism ; GPI-Linked Proteins ; Glycoproteins ; HeLa Cells ; Humans ; Immunity, Mucosal/*immunology ; Intestines/cytology ; Membrane Glycoproteins/*metabolism ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Peyer's Patches/*cytology/immunology ; Salmonella typhimurium/genetics/immunology/metabolism ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
    Location Call Number Expected Availability
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