Studies on bacterial chemotaxis. VI. Effect of cheX mutation on the methylation of methyl-accepting chemotaxis protein of Escherichia coli.

A membrane from Escherichia coli cheX mutants failed to accept the methyl-moiety when incubated with a cytoplasm of wild type bacteria. The possibility of reduced production of methyl-accepting chemotaxis protein (MCP) as a result of the effect of cheX mutation was considered. However, analysis of sulfur labeled proteins from cheX mutants by two-dimensional gel electrophoresis showed that the proportion of non-esterified MCP increased in cheX mutants while the total amount of MCP was not seriously affected. Thus the decreased methylation of MCP in cheX mutants, as detected by the methyl-labeling experiment, is not caused by an effect of cheX mutation on the production of MCP back-bone protein but by a defect in the device for methylation. The presence of four species of MCP's whose extent of methylation was affected by cheX mutation as well as cheB mutation was also shown by this experiment.