title: Multiple forms of the CheB methylesterase in bacterial chemosensing.
abstract: The methylesterase which catalyzes demethylation of chemotactic membrane receptors in Salmonella typhimurium has been purified and characterized. Two forms of the enzyme have been isolated from cell extracts. One corresponds in molecular weight, Mr = 37,000, and amino acid composition to the predicted product of the structural gene for the methylesterase, cheB. The other is a proteolytic fragment, Mr = 21,000, corresponding to the C-terminal three-fifths of the intact CheB protein. The specific activity of the 21-kDa enzyme is at least 15-fold greater than that of its 37-kDa precursor. We conclude that the CheB protein is composed of at least two structurally distinct portions: a C-terminal catalytic domain, and an N-terminal region which modulates esterase activity.
authors.forename: S A
authors.initials: SA
authors.lastname: Simms
authors.forename: M G
authors.initials: MG
authors.lastname: Keane
authors.forename: J
authors.initials: J
authors.lastname: Stock
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D002633:Chemotaxis; D004262:DNA Restriction Enzymes; D004789:Enzyme Activation; D005796:Genes; D005798:Genes, Bacterial; D007700:Kinetics; D008970:Molecular Weight; D010957:Plasmids; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics; D014357:Trypsin / Q000378:metabolism
chemical_list: D002265:Carboxylic Ester Hydrolases; C041144:chemotactic protein methylesterase; D004262:DNA Restriction Enzymes; D014357:Trypsin