Abstract
Chemotactic responses in motile bacteria are the result of sophisticated signal transduction by large, highly organized arrays of sensory proteins. Despite tremendous progress in the understanding of chemosensory array structure and function, a structural basis for the heightened sensitivity of networked chemoreceptors is not yet complete. Here, we present cryo-electron tomography visualisations of native-state chemosensory arrays in E. coli minicells. Strikingly, these arrays appear to exhibit a p2-symmetric array architecture that differs markedly from the p6-symmetric architecture previously described in E. coli. Based on this data, we propose molecular models of this alternative architecture and the canonical p6-symmetric assembly. We evaluate our observations and each model in the context of previously published data, assessing the functional implications of an alternative architecture and effects for future studies.
Highlights
Chemotactic responses in motile bacteria are the result of sophisticated signal transduction by large, highly organized arrays of sensory proteins
Chemotactic responses in bacteria are mediated by large protein complexes known as chemosensory arrays, comprising thousands of copies of three primary components: transmembrane chemoreceptors
First visualized by negative stain electron microscopy [11], the striking extended architecture of chemosensory arrays was immediately identified as an ideal target for cryoelectron microscopy [12] and cryo-electron tomography [13,14]
Summary
Chemotactic responses in motile bacteria are the result of sophisticated signal transduction by large, highly organized arrays of sensory proteins. We present cryo-electron tomography visualisations of native-state chemosensory arrays in E. coli minicells. These arrays appear to exhibit a p2-symmetric array architecture that differs markedly from the p6-symmetric architecture previously described in E. coli. Subsequent cryo-ET studies, informed by crystal structures and molecular modelling, revealed the organisation of the baseplate region containing CheA and CheW in E. coli [18,19], describing the existence of six-membered (A.P5/W) rings involving the CheA P5 regulatory domain (A.P5) and Academic Editor: Cristina Martínez-Villaluenga
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