CheZ mutants with enhanced ability to dephosphorylate CheY, the response regulator in bacterial chemotaxis.
CheZ is a component of the chemotaxis signal-transduction pathway in Escherichia coli and Salmonella typhimurium. It is responsible for accelerating dephosphorylation of CheY and thereby antagonizing the tumble-promoting activity of CheY. In the absence of functional CheZ, cells are non-chemotactic and tumble constantly. We characterized the effects of two mutations in CheZ, R54C and V166G, that are unusual in that they cause cells to have a smooth swimming bias. These mutations were isolated as second-site suppressors of mutations in the switch complex responsible for regulating the direction of flagellar rotation (Yamaguchi, S., Aizawa, S.-I., Kihara, M. Isomura, M., Jones, C.J. and Macnab, R.M. (1986) J. Bacteriol. 168, 1172-1179). When produced at low levels in a delta cheZ host strain, CheZ R54C and CheZ V166G supported chemotaxis. However, when moderately overproduced they markedly inhibited chemotactic ability. In vitro studies revealed that these mutations enhanced the ability of CheZ to accelerate dephosphorylation of CheY. These results are discussed in relation to the possible roles and interactions of CheZ in the chemotaxis system.
Department of Microbiology and Immunology, McGill University, Montreal, Québec, Canada.
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D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002633:Chemotaxis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D015183:Restriction Mapping; D012486:Salmonella typhimurium / Q000235:genetics
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; C000607606:cheY protein, E coli