title: Structure of bacterial cytoplasmic chemoreceptor arrays and implications for chemotactic signaling.
abstract: Most motile bacteria sense and respond to their environment through a transmembrane chemoreceptor array whose structure and function have been well-studied, but many species also contain an additional cluster of chemoreceptors in their cytoplasm. Although the cytoplasmic cluster is essential for normal chemotaxis in some organisms, its structure and function remain unknown. Here we use electron cryotomography to image the cytoplasmic chemoreceptor cluster in Rhodobacter sphaeroides and Vibrio cholerae. We show that just like transmembrane arrays, cytoplasmic clusters contain trimers-of-receptor-dimers organized in 12-nm hexagonal arrays. In contrast to transmembrane arrays, however, cytoplasmic clusters comprise two CheA/CheW baseplates sandwiching two opposed receptor arrays. We further show that cytoplasmic fragments of normally transmembrane E. coli chemoreceptors form similar sandwiched structures in the presence of molecular crowding agents. Together these results suggest that the 12-nm hexagonal architecture is fundamentally important and that sandwiching and crowding can replace the stabilizing effect of the membrane. DOI: http://dx.doi.org/10.7554/eLife.02151.001.
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States.
authors.forename: Ariane
authors.initials: A
authors.lastname: Briegel
authors.forename: Mark S
authors.initials: MS
authors.lastname: Ladinsky
authors.forename: Catherine
authors.initials: C
authors.lastname: Oikonomou
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Jones
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Harris
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fowler
authors.forename: Yi-Wei
authors.initials: YW
authors.lastname: Chang
authors.forename: Lynmarie K
authors.initials: LK
authors.lastname: Thompson
authors.forename: Judith P
authors.initials: JP
authors.lastname: Armitage
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
mesh_terms: D002628:Chemoreceptor Cells / Q000378:metabolism*; D002633:Chemotaxis; D003593:Cytoplasm / Q000378:metabolism*; D019281:Dimerization; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D015398:Signal Transduction; D014054:Tomography / Q000379:methods; D014734:Vibrio cholerae / Q000378:metabolism*
keywords: Rhodobacter sphaeroides; Vibrio cholerae; chemotaxis; correlative microscopy; electron cryotomography