SecB-like chaperone controls a toxin–antitoxin stress-responsive system in Mycobacterium tuberculosis
结核分支杆菌中SecB类似的分子伴侣调控一个毒素-抗毒素胁迫反应性系统
towersimper 译
SecB-like chaperone controls a toxin–antitoxin stress-responsive system in Mycobacterium tuberculosis 于2011年5月2日发布在PNAS杂志网络上。
细菌新合成的蛋白前体在生物产生过程中一个重要的步骤就是将它们运输到内膜的Sec转位子(translocon，也称为转位酶,translocase)。在革兰氏阴性细菌中，分子伴侣SecB结合到蛋白前体的非天然形式(nonnative forms)，特异性地将它们转移到转位酶的动力组分SecA，从而促进它们输出。
一个主要的人类致病菌结核分支杆菌(Mycobacterium tuberculosis)是一个不同寻常的革兰氏阳性细菌，具有明确的外膜和外膜蛋白。在这个细菌中，辅助前体蛋白的分子伴侣依然还未被搜寻到。本文，研究人员证实结核分支杆菌中未被定义描述的Rv1957基因能够替换大肠杆菌(Escherichia coli)中的SecB功能，阻止体外前体蛋白(preprotein)聚集。有意思地说，在结核分支杆菌中，Rv1957与一个功能性的胁迫反应性(stress-responsive)的higB-higA毒素-抗毒素(toxin-antitoxin,TA)位点簇集在一起，尽管该位点的功能还不明确。进一步的大肠杆菌和没有TA-分子伴侣位点的海分枝杆菌(Mycobacterium marinum)体内实验表明当抗毒素和分子伴侣联合表达时，该毒素的严重毒性被完全抑制。研究人员还发现Rv1957通过阻止抗毒素聚集和降解直接作用在抗毒素上。
归纳在一起，这些研究结果表明SecB类似的分子伴侣Rv1957特异性地调控一个胁迫反应性的TA系统，该系统与结核分支杆菌的适应性反应相关。\\生命科学论坛\\ towersimper
towersimper博文：http://bbs.bioon.net/bbs/home.php?mod=space&uid=139460&do=blog&id=90204
注：版权所有，欢迎转载，转载请注明来源作者。
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1101189108
SecB-like chaperone controls a toxin–antitoxin stress-responsive system in Mycobacterium tuberculosis
Patricia Bordes, Anne-Marie Cirinesi, Roy Ummels, Ambre Sala, Samer Sakr, Wilbert Bitter, and Pierre Genevaux
Edited by Linda L. Randall, University of Missouri, Columbia, MO, and approved April 12, 2011 (received for review January 22, 2011)
[Abstract]
A major step in the biogenesis of newly synthesized precursor proteins in bacteria is their targeting to the Sec translocon at the inner membrane. In Gram-negative bacteria, the chaperone SecB binds nonnative forms of precursors and specifically transfers them to the SecA motor component of the translocase, thus facilitating their export. The major human pathogen Mycobacterium tuberculosis is an unusual Gram-positive bacterium with a well-defined outer membrane and outer membrane proteins. Assistance to precursor proteins by chaperones in this bacterium remains largely unexplored. Here we show that the product of the previously uncharacterized Rv1957 gene of M. tuberculosis can substitute for SecB functions in Escherichia coli and prevent preprotein aggregation in vitro. Interestingly, in M. tuberculosis, Rv1957 is clustered with a functional stress-responsive higB-higA toxin–antitoxin (TA) locus of unknown function. Further in vivo experiments in E. coli and in Mycobacterium marinum strains that do not possess the TA-chaperone locus show that the severe toxicity of the toxin was entirely inhibited when the antitoxin and the chaperone were jointly expressed. We found that Rv1957 acts directly on the antitoxin by preventing its aggregation and protecting it from degradation. Taken together, our results show that the SecB-like chaperone Rv1957 specifically controls a stress-responsive TA system relevant for M. tuberculosis adaptive response.(http://www.pnas.org/content/early/2011/04/27/1101189108.abstract)
