title: Kinase-active signaling complexes of bacterial chemoreceptors do not contain proposed receptor-receptor contacts observed in crystal structures.
abstract: The receptor dimers that mediate bacterial chemotaxis form high-order signaling complexes with CheW and the kinase CheA. From the packing arrangement in two crystal structures of different receptor cytoplasmic fragments, two different models have been proposed for receptor signaling arrays: the trimers-of-dimers and hedgerow models. Here we identified an interdimer distance that differs substantially in the two models, labeled the atoms defining this distance through isotopic enrichment, and measured it with (19)F-(13)C REDOR. This was done in two types of receptor samples: isolated bacterial membranes containing overexpressed, intact receptor and soluble receptor fragments reconstituted into kinase-active signaling complexes. In both cases, the distance found was not compatible with the receptor dimer-dimer contacts observed in the trimers-of-dimers or in the hedgerow models. Comparisons of simulated and observed REDOR dephasing were used to deduce a closest approach distance at this interface, which provides a constraint for the possible arrangements of receptor assemblies.
authors.affiliation: Department of Chemistry, 710 North Pleasant Street, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fowler
authors.forename: Robert M
authors.initials: RM
authors.lastname: Weis
authors.forename: Lynmarie K
authors.initials: LK
authors.lastname: Thompson
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002633:Chemotaxis / Q000235:genetics; D003198:Computer Simulation; D003460:Crystallization; D019281:Dimerization; D004789:Enzyme Activation; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D000071677:Histidine Kinase; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D000072236:Methyl-Accepting Chemotaxis Proteins; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010649:Phenylalanine / Q000737:chemistry; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D020239:Receptor Cross-Talk; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction / Q000502:physiology; D020124:Thermotoga maritima / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D012694:Serine; D010649:Phenylalanine; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli