title: The methyl-accepting chemotaxis proteins of E. coli: a repellent-stimulated, covalent modification, distinct from methylation.
abstract: The methyl-accepting chemotaxis proteins (MCPs) of Escherichia coli are integral membrane proteins that have been shown to undergo reversible methylation in response to the addition of attractants. We have shown that a second, rapid modification of MCPI and MCPII occurs, which is repellent-stimulated. This modification, which is not methylation, was detected because it causes a decrease in mobility of the MCPs on 7.5% SDS-polyacrylamide gels with a high acrylamide to bisacrylamide ratio. We have designated this modification as the CheB-modification, as it is dependent on the CheB gene product. The CheB-modification causes a decrease in the isoelectric point of MCPII by one or two charge groups. The CheB-modification is not necessary for the methylation, nor does it preclude methylation of the MCPs. Both the CheB-modified form and the unmodified, unmethylated forms of the MCPs are stable to treatment with base, which results in the hydrolysis of the methylesters (demethylation) of the MCPs. The potential role of CheB-modification in chemotaxis is discussed.
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D055598:Chemical Phenomena; D002621:Chemistry; D002630:Chemotactic Factors / Q000032:analysis*; D002633:Chemotaxis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000032:analysis* / Q000235:genetics; D005798:Genes, Bacterial; D007526:Isoelectric Point; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D008745:Methylation
chemical_list: D001426:Bacterial Proteins; D002630:Chemotactic Factors; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins