In situ structure of the Caulobacter crescentus flagellar motor and visualization of binding of a CheY‐homolog. Issue 3 (25th May 2020)

• Record Type: Journal Article
• Authors: Rossmann, Florian M.; Hug, Isabelle; Sangermani, Matteo; Jenal, Urs; Beeby, Morgan
• Is Part Of: Molecular microbiology. Volume 114:Issue 3(2020)
• Page Start: 443
• Page End: 453
• Publication Date: 2020-05-25
• Subjects: Caulobacter crescentus -- CheY -- cyclic‐di‐GMP -- effector binding -- subtomogram averaging; Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.14525
• Languages: English
• ISSNs: 0950-382X

Abstract

Abstract: Bacterial flagellar motility is controlled by the binding of CheY proteins to the cytoplasmic switch complex of the flagellar motor, resulting in changes in swimming speed or direction. Despite its importance for motor function, structural information about the interaction between effector proteins and the motor are scarce. To address this gap in knowledge, we used electron cryotomography and subtomogram averaging to visualize such interactions inside Caulobacter crescentus cells. In C. crescentus, several CheY homologs regulate motor function for different aspects of the bacterial lifestyle. We used subtomogram averaging to image binding of the CheY family protein CleD to the cytoplasmic Cring switch complex, the control center of the flagellar motor. This unambiguously confirmed the orientation of the motor switch protein FliM and the binding of a member of the CheY protein family to the outside rim of the C ring. We also uncovered previously unknown structural elaborations of the alphaproteobacterial flagellar motor, including two novel periplasmic ring structures, and the stator ring harboring eleven stator units, adding to our growing catalog of bacterial flagellar diversity. Abstract : The flagellar motor is a tiny bacterial nanomachine that needs to carefully respond to the bacterium's surroundings. We determined the first molecular structure of a flagellar motor with a bound regulatory protein inside a living Caulobacter crescentus cell. We also discovered intriguing new features of the flagellar motor from this bacterium with unknown roles. Our findings will help us to understand how nanomachines can be controlled at a molecular level.