Smith Margaret A, Clemons William M, DeMars Cathrine J, Flower Ann M
Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202-9037, USA.
J Bacteriol. 2005 Sep;187(18):6454-65. doi: 10.1128/JB.187.18.6454-6465.2005.
The apparatus responsible for translocation of proteins across bacterial membranes is the conserved SecY complex, consisting of SecY, SecE, and SecG. Prior genetic analysis provided insight into the mechanisms of protein export, as well as the interactions between the component proteins. In particular, the prl suppressor alleles of secE and secY, which allow export of secretory proteins with defective signal sequences, have proven particularly useful. Here, we report the isolation of novel mutations in secE and secY, as well as the phenotypic effects of combinations of prl mutations. These new alleles, as well as previously characterized prl mutations, were analyzed in light of the recently published crystal structure of the archaeal SecY complex. Our results support and expand a model of Prl suppressor activity that proposes that all of the prlA and prlG alleles either destabilize the closed state of the channel or stabilize the open form. These mutants thus allow channel opening to occur without the triggering event of signal sequence binding that is required in a wild-type complex.
负责蛋白质跨细菌膜转运的装置是保守的SecY复合体，由SecY、SecE和SecG组成。先前的遗传学分析深入了解了蛋白质输出机制以及组成蛋白之间的相互作用。特别是，secE和secY的prl抑制子等位基因可使信号序列有缺陷的分泌蛋白输出，已证明其特别有用。在此，我们报告了secE和secY中新突变的分离以及prl突变组合的表型效应。根据最近发表的古细菌SecY复合体晶体结构，对这些新等位基因以及先前表征的prl突变进行了分析。我们的结果支持并扩展了Prl抑制子活性模型，该模型提出所有prlA和prlG等位基因要么使通道的关闭状态不稳定，要么使开放形式稳定。因此，这些突变体允许通道开放，而无需野生型复合体中所需的信号序列结合触发事件。
