Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, South Yorkshire, UK.
Current address: Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
Sci Rep. 2021 Mar 19;11(1):6447. doi: 10.1038/s41598-021-85726-0.
Tripartite members of the ClyA family of α-PFTs have recently been identified in a number of pathogenic Gram-negative bacteria, including the human pathogen Serratia marcescens. Structures of a Gram-negative A component and a tripartite α-PFT complete pore are unknown and a mechanism for pore formation is still uncertain. Here we characterise the tripartite SmhABC toxin from S. marcescens and propose a mechanism of pore assembly. We present the structure of soluble SmhA, as well as the soluble and pore forms of SmhB. We show that the β-tongue soluble structure is well conserved in the family and propose two conserved latches between the head and tail domains that are broken on the soluble to pore conformational change. Using the structures of individual components, sequence analysis and docking predictions we illustrate how the A, B and C protomers would assemble on the membrane to produce a complete tripartite α-PFT pore.
三部分 ClyA 家族的 α-PFT 最近在许多致病性革兰氏阴性菌中被发现，包括人类病原体粘质沙雷氏菌。革兰氏阴性 A 成分和三部分 α-PFT 完整孔的结构尚不清楚，孔形成的机制仍不确定。在这里，我们描述了来自粘质沙雷氏菌的三部分 SmhABC 毒素，并提出了一种孔组装的机制。我们展示了可溶性 SmhA 的结构，以及 SmhB 的可溶性和孔形式。我们表明，家族中的 β-舌可溶性结构得到了很好的保守，并提出了头部和尾部之间的两个保守闩锁，在可溶性到孔构象变化时被打破。利用单个组件的结构、序列分析和对接预测，我们说明了 A、B 和 C 原聚体如何在膜上组装以产生完整的三部分 α-PFT 孔。
