Identification of a protein methyltransferase as the cheR gene product in the bacterial sensing system.

Abstract

Methylation of membrane-bound proteins with apparent MW of .apprx. 65,000 does not occur in mutants of the generally nonchemotactic cheR class of Salmonella typhimurium. This is due to the lack of a protein methyltransferase in these mutants as shown by an in vitro assay using soluble proteins, membranes and S-adenosylmethionine as the methyl donor. The methylase from the wild type was purified, characterized and had a MW of 38,000. It is specific for proteins in S. typhimurium and Escherichia coli membranes. The methylase is not required for tumbling but appears to be essential for maintaining the appropriate rate constants and levels of the regulator of the chemotactic response.