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<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">C-Terminal Charged Cluster of MscL, RKKEE, Functions as a pH Sensor</title><author><name sortKey="Kloda, Anna" sort="Kloda, Anna" uniqKey="Kloda A" first="Anna" last="Kloda">Anna Kloda</name><affiliation><nlm:aff wicri:cut="; and" id="N0x9cba368.0x8b9e718">School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia</nlm:aff></affiliation></author><author><name sortKey="Ghazi, Alexandre" sort="Ghazi, Alexandre" uniqKey="Ghazi A" first="Alexandre" last="Ghazi">Alexandre Ghazi</name><affiliation><nlm:aff id="N0x9cba368.0x8b9e718">Laboratoire des Biomembranes, Unite Mixte de Recherche CNRS 8619, Universite Paris-Sud, 91405 Orsay Cedex, France</nlm:aff></affiliation></author><author><name sortKey="Martinac, Boris" sort="Martinac, Boris" uniqKey="Martinac B" first="Boris" last="Martinac">Boris Martinac</name><affiliation><nlm:aff wicri:cut="; and" id="N0x9cba368.0x8b9e718">School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia</nlm:aff></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">16387769</idno><idno type="pmc">1386778</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1386778</idno><idno type="RBID">PMC:1386778</idno><idno type="doi">10.1529/biophysj.105.075481</idno><date when="2005">2005</date><idno type="wicri:Area/Pmc/Corpus">000F65</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000F65</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">C-Terminal Charged Cluster of MscL, RKKEE, Functions as a pH Sensor</title><author><name sortKey="Kloda, Anna" sort="Kloda, Anna" uniqKey="Kloda A" first="Anna" last="Kloda">Anna Kloda</name><affiliation><nlm:aff wicri:cut="; and" id="N0x9cba368.0x8b9e718">School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia</nlm:aff></affiliation></author><author><name sortKey="Ghazi, Alexandre" sort="Ghazi, Alexandre" uniqKey="Ghazi A" first="Alexandre" last="Ghazi">Alexandre Ghazi</name><affiliation><nlm:aff id="N0x9cba368.0x8b9e718">Laboratoire des Biomembranes, Unite Mixte de Recherche CNRS 8619, Universite Paris-Sud, 91405 Orsay Cedex, France</nlm:aff></affiliation></author><author><name sortKey="Martinac, Boris" sort="Martinac, Boris" uniqKey="Martinac B" first="Boris" last="Martinac">Boris Martinac</name><affiliation><nlm:aff wicri:cut="; and" id="N0x9cba368.0x8b9e718">School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia</nlm:aff></affiliation></author></analytic><series><title level="j">Biophysical Journal</title><idno type="ISSN">0006-3495</idno><idno type="eISSN">1542-0086</idno><imprint><date when="2005">2005</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p>The RKKEE cluster of charged residues located within the cytoplasmic helix of the bacterial mechanosensitive channel, MscL, is essential for the channel function. The structure of MscL determined by x-ray crystallography and electron paramagnetic resonance spectroscopy has revealed discrepancies toward the C-terminus suggesting that the structure of the C-terminal helical bundle differs depending on the pH of the cytoplasm. In this study we examined the effect of pH as well as charge reversal and residue substitution within the RKKEE cluster on the mechanosensitivity of <italic>Escherichia coli</italic> MscL reconstituted into liposomes using the patch-clamp technique. Protonation of either positively or negatively charged residues within the cluster, achieved by changing the experimental pH or residue substitution within the RKKEE cluster, significantly increased the free energy of activation for the MscL channel due to an increase in activation pressure. Our data suggest that the orientation of the C-terminal helices relative to the aqueous medium is pH dependent, indicating that the RKKEE cluster functions as a proton sensor by adjusting the channel sensitivity to membrane tension in a pH-dependent fashion. A possible implication of our results for the physiology of bacterial cells is briefly discussed.</p></div></front></TEI><pmc article-type="research-article"><pmc-comment>The publisher of this article does not allow downloading of the full text in XML form.</pmc-comment>
<front><journal-meta><journal-id journal-id-type="nlm-ta">Biophys J</journal-id><journal-id journal-id-type="publisher-id">biophysj</journal-id><journal-title>Biophysical Journal</journal-title><issn pub-type="ppub">0006-3495</issn><issn pub-type="epub">1542-0086</issn><publisher><publisher-name>Biophysical Society</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="pmid">16387769</article-id><article-id pub-id-type="pmc">1386778</article-id><article-id pub-id-type="publisher-id">75481</article-id><article-id pub-id-type="doi">10.1529/biophysj.105.075481</article-id><article-categories><subj-group subj-group-type="heading"><subject>Channels, Receptors, and Electrical Signaling</subject></subj-group></article-categories><title-group><article-title>C-Terminal Charged Cluster of MscL, RKKEE, Functions as a pH Sensor</article-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>Kloda</surname><given-names>Anna</given-names></name><xref ref-type="aff" rid="N0x9cba368.0x8b9e718">*</xref></contrib><contrib contrib-type="author"><name><surname>Ghazi</surname><given-names>Alexandre</given-names></name><xref ref-type="aff" rid="N0x9cba368.0x8b9e718">†</xref></contrib><contrib contrib-type="author"><name><surname>Martinac</surname><given-names>Boris</given-names></name><xref ref-type="aff" rid="N0x9cba368.0x8b9e718">*</xref></contrib></contrib-group><aff id="N0x9cba368.0x8b9e718"><label>*</label>School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; and<label>†</label>Laboratoire des Biomembranes, Unite Mixte de Recherche CNRS 8619, Universite Paris-Sud, 91405 Orsay Cedex, France</aff><author-notes><fn><p>Address reprint requests to Dr. Boris Martinac, School of Biomedical Sciences, University of Queensland, Brisbane QLD 4072, Australia. Tel.: 61-7-3365-3113; Fax: 61-7-3365-1766; E-mail: <email>b.martinac@uq.edu.au</email>.</p></fn></author-notes><pub-date pub-type="ppub"><day>15</day><month>3</month><year>2006</year></pub-date><pub-date pub-type="epub"><day>30</day><month>12</month><year>2005</year></pub-date><volume>90</volume><issue>6</issue><fpage>1992</fpage><lpage>1998</lpage><history><date date-type="received"><day>3</day><month>10</month><year>2005</year></date><date date-type="accepted"><day>19</day><month>12</month><year>2005</year></date></history><copyright-statement>Copyright © 2006, Biophysical Society</copyright-statement><copyright-year>2006</copyright-year><abstract><p>The RKKEE cluster of charged residues located within the cytoplasmic helix of the bacterial mechanosensitive channel, MscL, is essential for the channel function. The structure of MscL determined by x-ray crystallography and electron paramagnetic resonance spectroscopy has revealed discrepancies toward the C-terminus suggesting that the structure of the C-terminal helical bundle differs depending on the pH of the cytoplasm. In this study we examined the effect of pH as well as charge reversal and residue substitution within the RKKEE cluster on the mechanosensitivity of <italic>Escherichia coli</italic> MscL reconstituted into liposomes using the patch-clamp technique. Protonation of either positively or negatively charged residues within the cluster, achieved by changing the experimental pH or residue substitution within the RKKEE cluster, significantly increased the free energy of activation for the MscL channel due to an increase in activation pressure. Our data suggest that the orientation of the C-terminal helices relative to the aqueous medium is pH dependent, indicating that the RKKEE cluster functions as a proton sensor by adjusting the channel sensitivity to membrane tension in a pH-dependent fashion. A possible implication of our results for the physiology of bacterial cells is briefly discussed.</p></abstract></article-meta></front></pmc></record>Pour manipuler ce document sous Unix (Dilib)
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