Structural control for the coordinated assembly into functional pathogenic type-3 secretion systems

作者：Nikolaus Goessweiner‐Mohr, Vadim Kotov, Matthias Brünner, Julia Mayr, Jiri Wald, Lucas Kuhlen, Sean Miletic, Oliver Vesper, Wolfgang Lugmayr, Samuel Wagner, Frank DiMaio, Susan M. Lea, Thomas C. Marlovits · 发表于：bioRxiv (Cold Spring Harbor Laboratory) · 年份：2019 · DOI：10.1101/714097 · 被引用次数：12 · 研究领域：Bacterial Genetics and Biotechnology、Bacteriophages and microbial interactions、Escherichia coli research studies

Abstract Functional injectisomes of the type-3 secretion system assemble into highly defined and stoichiometric bacterial molecular machines essential for infecting human and other eukaryotic cells. However, the mechanism that governs the regulated step-wise assembly process from the nucleation-phase, to ring-assembly, and the filamentous phase into a membrane embedded needle complex is unclear. We here report that the formation of a megadalton-sized needle complexes from Salmonella enterica serovar Typhimurium (SPI-1, Salmonella pathogenicity island-1) with proper stoichiometries is highly structurally controlled competing against the self-assembly propensity of injectisome components, leading to a highly unusual structurally-pleiotropic phenotype. The structure of the entire needle complex from pathogenic injectisomes was solved by cryo electron microscopy, focused refinements (2.5-4 Å) and co-variation analysis revealing an overall asymmetric arrangement containing cyclic, helical, and asymmetric sub-structures. The centrally located export apparatus assembles into a conical, pseudo-helical structure and provides a structural template that guides the formation of a 24-mer cyclic, surrounding ring, which then serves as a docking interface comprising three different conformations for sixteen N-terminal InvG subunits of the outer secretin ring. Unexpectedly, the secretin ring excludes the 16 th protein chain at the C-terminal outer ring, resulting in a pleiotropic 16/15-mer r...