Characterization of the chemotaxis protein CheW from Rhodobacter sphaeroides and its effect on the behaviour of Escherichia coli

Abstract

SummaryIn contrast to the situation in enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. A chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene. However, mutations in these genes have only minor effects on chemotaxis. In enteric species, CheW transmits sensory information from the chemoreceptors to the histidine protein kinase, CheA. Expression of R. sphaeroides cheW in Escherichia coli showed concentrationdependent inhibition of wild-type behaviour, increasing counter-clockwise rotation and thus smooth swimming -a phenotype also seen when E. coli cheW is overexpressed in E. coli. In contrast, overexpression of R. sphaeroides cheW in wild-type R. sphaeroides inhibited motility completely, the equivalent of inducing tumbly motility in E. coli. Expression of R. sphaeroides cheW in an E. coli ⌬cheW chemotaxis mutant complemented this mutation, confirming that CheW is involved in chemosensory signal transduction. However, unlike E. coli ⌬cheW mutants, inframe deletion of R. sphaeroides cheW did not affect either swimming behaviour or chemotaxis to weak organic acids, although the responses to sugars were enhanced. Therefore, although CheW may act as a signal-transduction protein in R. sphaeroides, it may have an unusual role in controlling the rotation of the flagellar motor. Furthermore, the ability of a ⌬cheW mutant to swim normally and show wild-type responses to weak acids supports the existence of additional chemosensory signal-transduction pathways.

Chemotaxis in the human gastric pathogen Helicobacter pylori: different roles for CheW and the three CheV paralogues, and evidence for CheV2 phosphorylation

“…This is the same effect seen upon overexpression of the homologous E. coli CheW (Sanders et al, 1989b). The production of a molar excess of CheW may result in inhibition of the interaction required to catalyse CheA autophosphorylation, possibly by excess CheW displacing the CheWCheA complex from the receptor (Hamblin et al, 1997). The result would be the formation of an inactive complex that cannot initiate the flow of phosphate to CheY.…”

“…This would reduce the levels of phospho-CheY, resulting in tumble suppression. Hamblin et al (1997) successfully complemented an E. coli ∆cheW mutant (RP4606) with cheW from Rhodobacter sphaeroides, which is a member of the α-subgroup of Proteobacteria. In contrast, the H. pylori cheW gene was apparently unable to complement RP4606.…”

A chemoreceptor from Pseudomonas putida forms active signalling complexes in Escherichia coli

“…Thus, there is no strict length-class specificity between receptors and the CheA kinase under their control. Likewise, the CheW coupling protein has been shown to be exchangeable between distantly related bacterial species (Alexandre & Zhulin, 2003;Hamblin et al, 1997).…”

Localization of MreB inRhodobacter sphaeroidesunder Conditions Causing Changes in Cell Shape and Membrane Structure

“…Constructs were sequenced to ensure that upstream and downstream regions were in frame and contained no errors. The constructs were introduced into R. sphaeroides by allelic exchange as described previously (8,19).…”