Structural basis of the bacterial flagellar motor rotational switching  

作　　者：Jiaxing Tan Ling Zhang Xingtong Zhou Siyu Han Yan Zhou Yongqun Zhu 

机构地区：[1]Department of Gastroenterology of the Second Affiliated Hospital,School of Medicine and College of Animal Sciences,Life Sciences Institute,Zhejiang University,Hangzhou,Zhejiang,China [2]The MOE Key Laboratory of Biosystems Homeostasis&Protection,and Zhejiang Provincial Key Laboratory of Cancer Molecular Cell Biology,Life Sciences Institute,Zhejiang University,Hangzhou,Zhejiang,China [3]Institute of Microbiology,College of Life Sciences,Zhejiang University,Hangzhou,Zhejiang,China [4]Shanghai Institute for Advanced Study,Zhejiang University,Shanghai,China [5]Cancer Center,Zhejiang University,Hangzhou,Zhejiang,China [6]Center for Veterinary Sciences,Department of Veterinary Medicine,College of Animal Sciences,Zhejiang University,Hangzhou,Zhejiang,China

出　　处：《Cell Research》2024年第11期788-801,共14页细胞研究（英文版）

基　　金：supported by grants from the National Natural Science Foundation of China(U23A20163 and 81925024);the National Key R&D Program of China(2017YFA0503900);the Fundamental Research Funds for the Central Universities;Y.Zhu and Y.Zhou were supported by National High-level Talents Special Support Program of China.

摘　　要：The bacterial flagellar motor is a huge bidirectional rotary nanomachine that drives rotation of the flagellum for bacterial motility.The cytoplasmic C ring of the flagellar motor functions as the switch complex for the rotational direction switching from counterclockwise to clockwise.However,the structural basis of the rotational switching and how the C ring is assembled have long remained elusive.Here,we present two high-resolution cryo-electron microscopy structures of the C ring-containing flagellar basal body–hook complex from Salmonella Typhimurium,which are in the default counterclockwise state and in a constitutively active CheY mutant-induced clockwise state,respectively.In both complexes,the C ring consists of four subrings,but is in two different conformations.The CheY proteins are bound into an open groove between two adjacent protomers on the surface of the middle subring of the C ring and interact with the FliG and FliM subunits.The binding of the CheY protein induces a significant upward shift of the C ring towards the MS ring and inward movements of its protomers towards the motor center,which eventually remodels the structures of the FliG subunits and reverses the orientations and surface electrostatic potential of theαtorque helices to trigger the counterclockwise-to-clockwise rotational switching.The conformational changes of the FliG subunits reveal that the stator units on the motor require a relocation process in the inner membrane during the rotational switching.This study provides unprecedented molecular insights into the rotational switching mechanism and a detailed overall structural view of the bacterial flagellar motors.

关 键 词：ROTATIONAL eventually DEFAULT 

分 类 号：R363[医药卫生—病理学]