Structure of the native supercoiled flagellar hook as a universal joint

Takayuki Kato,Tomoko Miyata,Keiichi Namba,Fumiaki Makino,Péter Horváth

doi:10.1038/s41467-019-13252-9

Abstract

The Bacterial flagellar hook is a short supercoiled tubular structure made from a helical assembly of the hook protein FlgE. The hook acts as a universal joint that connects the flagellar basal body and filament, and smoothly transmits torque generated by the rotary motor to the helical filament propeller. In peritrichously flagellated bacteria, the hook allows the filaments to form a bundle behind the cell for swimming, and for the bundle to fall apart for tumbling. Here we report a native supercoiled hook structure at 3.6 Å resolution by cryoEM single particle image analysis of the polyhook. The atomic model built into the three-dimensional (3D) density map reveals the changes in subunit conformation and intersubunit interactions that occur upon compression and extension of the 11 protofilaments during their smoke ring-like rotation. These observations reveal how the hook functions as a dynamic molecular universal joint with high bending flexibility and twisting rigidity.

Highlights

The Bacterial flagellar hook is a short supercoiled tubular structure made from a helical assembly of the hook protein FlgE
The basal body acts as a rotary motor powered by ion motive force across the cytoplasmic membrane as well as a protein export apparatus to construct the axial structure of the flagellum
The atomic model of Salmonella straight hook became more complete and reliable several years later by a higher-resolution 3D density map obtained by advanced techniques of cryoEM helical image analysis that made it possible to visualize most of the secondary structures of subunit proteins within a week or so from data collection to image analysis[9]

Summary

Introduction

The atomic model built into the threedimensional (3D) density map reveals the changes in subunit conformation and intersubunit interactions that occur upon compression and extension of the 11 protofilaments during their smoke ring-like rotation These observations reveal how the hook functions as a dynamic molecular universal joint with high bending flexibility and twisting rigidity. The atomic model built into the density map shows the actual changes in subunit conformation and 7 intersubunit interactions upon compression and extension of the 11 protofilaments that occur during their smoke ring-like rotation and allow the hook to function as a dynamic molecular universal joint with high bending flexibility and twisting rigidity

Methods

Results

Conclusion