Laboratoire de Microbiologie et Génétique Moléculaire, Centre National de la Recherche Scientifique, Université Paul Sabatier, Toulouse, France.
Front Microbiol. 2014 Dec 5;5:666. doi: 10.3389/fmicb.2014.00666. eCollection 2014.
Protein export in bacteria is facilitated by the canonical SecB chaperone, which binds to unfolded precursor proteins, maintains them in a translocation competent state and specifically cooperates with the translocase motor SecA to ensure their proper targeting to the Sec translocon at the cytoplasmic membrane. Besides its key contribution to the Sec pathway, SecB chaperone tasking is critical for the secretion of the Sec-independent heme-binding protein HasA and actively contributes to the cellular network of chaperones that control general proteostasis in Escherichia coli, as judged by the significant interplay found between SecB and the trigger factor, DnaK and GroEL chaperones. Although SecB is mainly a proteobacterial chaperone associated with the presence of an outer membrane and outer membrane proteins, secB-like genes are also found in Gram-positive bacteria as well as in certain phages and plasmids, thus suggesting alternative functions. In addition, a SecB-like protein is also present in the major human pathogen Mycobacterium tuberculosis where it specifically controls a stress-responsive toxin-antitoxin system. This review focuses on such very diverse chaperone functions of SecB, both in E. coli and in other unrelated bacteria.
细菌中的蛋白输出是由典型的 SecB 伴侣协助完成的，它与未折叠的前体蛋白结合，使其保持在易位状态，并与易位马达 SecA 特异性合作，以确保它们正确靶向细胞质膜上的 Sec 易位通道。除了对 Sec 途径的关键贡献外，SecB 伴侣的任务对于 Sec 独立的血红素结合蛋白 HasA 的分泌也是至关重要的，并通过 SecB 与触发因子、DnaK 和 GroEL 伴侣之间发现的显著相互作用，积极参与到控制大肠杆菌一般蛋白质稳态的伴侣细胞网络中。尽管 SecB 主要是一种与外膜和外膜蛋白存在相关的变形菌伴侣，但 secB 样基因也存在于革兰氏阳性菌以及某些噬菌体和质粒中，因此暗示了其具有替代功能。此外，SecB 样蛋白也存在于主要的人类病原体结核分枝杆菌中，它特异性地控制应激反应性毒素-抗毒素系统。这篇综述重点介绍了 SecB 在大肠杆菌和其他不相关细菌中的这些非常多样化的伴侣功能。
