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Published March 18, 2014 | Erratum + Supplemental Material + Published
Journal Article Open

New Insights into Bacterial Chemoreceptor Array Structure and Assembly from Electron Cryotomography

Abstract

Bacterial chemoreceptors cluster in highly ordered, cooperative, extended arrays with a conserved architecture, but the principles that govern array assembly remain unclear. Here we show images of cellular arrays as well as selected chemoreceptor complexes reconstituted in vitro that reveal new principles of array structure and assembly. First, in every case, receptors clustered in a trimers-of-dimers configuration, suggesting this is a highly favored fundamental building block. Second, these trimers-of-receptor dimers exhibited great versatility in the kinds of contacts they formed with each other and with other components of the signaling pathway, although only one architectural type occurred in native arrays. Third, the membrane, while it likely accelerates the formation of arrays, was neither necessary nor sufficient for lattice formation. Molecular crowding substituted for the stabilizing effect of the membrane and allowed cytoplasmic receptor fragments to form sandwiched lattices that strongly resemble the cytoplasmic chemoreceptor arrays found in some bacterial species. Finally, the effective determinant of array structure seemed to be CheA and CheW, which formed a "superlattice" of alternating CheA-filled and CheA-empty rings that linked receptor trimers-of-dimer units into their native hexagonal lattice. While concomitant overexpression of receptors, CheA, and CheW yielded arrays with native spacing, the CheA occupancy was lower and less ordered, suggesting that temporal and spatial coordination of gene expression driven by a single transcription factor may be vital for full order, or that array overgrowth may trigger a disassembly process. The results described here provide new insights into the assembly intermediates and assembly mechanism of this massive macromolecular complex.

Additional Information

© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: January 14, 2014. Revised: February 28, 2014. Publication Date (Web): February 28, 2014. Funding: This work was supported by National Institutes of Health Grant R01-GM085288 to L.K.T., National Institute of General Medical Sciences Grant GM101425 to G.J.J., National Institutes of Health Grant R01-GM040731 to J.J.F., National Institutes of Health Grant RO1-GM055984 to L.L.K., and National Institutes of Health CBI training grant T32 GM008505 to H.L.H. We thank Drs. Zhiheng Yu and Jason de la Cruz for microscopy support at Howard Hughes Medical Institute Janelia Farms and Dr. Dan Toso and Associate Director Ivo Atanasov for support using the University of California TITAN Krios microscope. We thank Drs. Gongpu Zhao and Peijun Zhang for initial electron micrographs of the PEG-mediated complexes of CF, CheA, and CheW. We thank Dr. Sandy Parkinson for the gift of α-Tsr and α-CheA antibodies, strains, and plasmids, as well as for sharing results prior to publication. We thank Dr. John Heumann for assistance with PEET software.

Attached Files

Published - bi5000614.pdf

Supplemental Material - bi5000614_si_001.pdf

Supplemental Material - bi5000614_si_002.mov

Erratum - bi501167j.pdf

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Created:
August 20, 2023
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October 20, 2023