Lilic Mirjana, Quezada Cindy M, Stebbins C Erec
Laboratory of Structural Microbiology, The Rockefeller University, New York, NY 10065, USA.
Acta Crystallogr D Biol Crystallogr. 2010 Jun;66(Pt 6):709-13. doi: 10.1107/S0907444910010796. Epub 2010 May 15.
Protein type III secretion systems (T3SSs) are organic nanosyringes that achieve an energy-dependent translocation of bacterial proteins through the two membranes of Gram-negative organisms. Examples include the pathogenic systems of animals, plants and symbiotic bacteria that inject factors into eukaryotic cells, and the flagellar export system that secretes flagellin. T3SSs possess a core of several membrane-associated proteins that are conserved across all known bacterial species that use this system. The Salmonella protein InvA is one of the most highly conserved proteins of this core of critical T3SS components. The crystal structure of a C-terminal domain of InvA reveals an unexpected homology to domains that have been repeatedly found as building blocks of other elements of the T3SS apparatus. This suggests the surprising hypothesis that evolution has produced a significant component of the apparatus structure through a series of gene-duplication and gene-rearrangement events.
III型蛋白分泌系统（T3SSs）是一种有机纳米注射器，可通过革兰氏阴性菌的两层膜实现细菌蛋白的能量依赖性转运。例如，动物、植物和共生细菌的致病系统会将因子注入真核细胞，鞭毛输出系统则会分泌鞭毛蛋白。T3SSs拥有几个与膜相关的核心蛋白，在所有已知使用该系统的细菌物种中都是保守的。沙门氏菌蛋白InvA是这个关键T3SS组件核心中最保守的蛋白之一。InvA C端结构域的晶体结构揭示了与其他T3SS装置元件反复发现的结构域存在意外的同源性。这表明了一个令人惊讶的假设，即进化通过一系列基因复制和基因重排事件产生了该装置结构的一个重要组成部分。
