Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536.
Proc Natl Acad Sci U S A. 2022 Dec 20;119(51):e2218010119. doi: 10.1073/pnas.2218010119. Epub 2022 Dec 13.
Type III secretion systems are bacterial nanomachines specialized in protein delivery into target eukaryotic cells. The structural and functional complexity of these machines demands highly coordinated mechanisms for their assembly and operation. The sorting platform is a critical component of type III secretion machines that ensures the timely engagement and secretion of proteins destined to travel this export pathway. However, the mechanisms that lead to the assembly of this multicomponent structure have not been elucidated. Herein, employing an extensive in vivo cross-linking strategy aided by structure modeling, we provide a detailed intersubunit contact survey of the entire sorting platform complex. Using the identified cross-links as signatures for pairwise intersubunit interactions in combination with systematic genetic deletions, we mapped the assembly process of this unique bacterial structure. Insights generated by this study could serve as the bases for the rational development of antivirulence strategies to combat several medically important bacterial pathogens.
III 型分泌系统是一类专门将蛋白质输送到靶真核细胞的细菌纳米机器。这些机器的结构和功能的复杂性要求其组装和运行需要高度协调的机制。分选平台是 III 型分泌机器的关键组成部分，可确保及时参与和分泌要通过此出口途径运输的蛋白质。然而，导致组装这种多组件结构的机制尚未阐明。在此，我们通过结构建模辅助的广泛体内交联策略，提供了整个分选平台复合物的详细亚基间接触调查。我们使用鉴定的交联作为标记，结合系统的遗传缺失，来映射这个独特细菌结构的组装过程。这项研究产生的见解可以为合理开发抗毒力策略以对抗几种具有重要医学意义的细菌病原体提供基础。
