Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada; email:
Current affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA.
Annu Rev Microbiol. 2023 Sep 15;77:669-698. doi: 10.1146/annurev-micro-032521-025503.
Two of the most fascinating bacterial nanomachines-the broadly disseminated rotary flagellum at the heart of cellular motility and the eukaryotic cell-puncturing injectisome essential to specific pathogenic species-utilize at their core a conserved export machinery called the type III secretion system (T3SS). The T3SS not only secretes the components that self-assemble into their extracellular appendages but also, in the case of the injectisome, subsequently directly translocates modulating effector proteins from the bacterial cell into the infected host. The injectisome is thought to have evolved from the flagellum as a minimal secretory system lacking motility, with the subsequent acquisition of additional components tailored to its specialized role in manipulating eukaryotic hosts for pathogenic advantage. Both nanomachines have long been the focus of intense interest, but advances in structural and functional understanding have taken a significant step forward since 2015, facilitated by the revolutionary advances in cryo-electron microscopy technologies. With several seminal structures of each nanomachine now captured, we review here the molecular similarities and differences that underlie their diverse functions.
两种最引人入胜的细菌纳米机器——细胞运动核心的广泛传播的旋转鞭毛和真核细胞刺穿注射器——都利用了一种被称为 III 型分泌系统（T3SS）的保守输出机制。T3SS 不仅分泌自我组装成细胞外附属物的组件，而且在注射器的情况下，随后直接将调节效应蛋白从细菌细胞转运到感染的宿主中。注射器被认为是从鞭毛进化而来的，是一种缺乏运动能力的最小分泌系统，随后获得了更多的组件，以适应其在操纵真核宿主以获得致病性优势方面的特殊作用。这两种纳米机器一直是人们关注的焦点，但自 2015 年以来，随着冷冻电子显微镜技术的革命性进步，在结构和功能理解方面取得了重大进展。现在已经捕获了这两种纳米机器的几个重要结构，我们在这里回顾了它们不同功能的分子相似性和差异性。
