Methylation of chemotaxis-specific proteins in Escherichia coli cells permeable to S-adenosylmethionine

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Abstract
Using a modification of the EGTA [ethylenglycol-bis(.beta.-aminoethylether)N,N,N'',N''-tetraacetate] treatment of Oishi and Smith E. coli cells were made permeable to S-adenosylmethionine and other related molecules to facilitate the study of methylation in chemotaxis. The permeable cells are nonmotile but respond to chemotactic stimuli by reversible methylation of their methyl-accepting chemotactic proteins (MCP I and MCP II) in a manner similar to that of untreated, motile cells. Addition of S-adenosyl-L-[methyl-3H]methionine to the permeable cells specifically labels 2 proteins, MCP I and MCP II. Methylation of these MCP is dependent on the presence of wild-type gene products of flaI, flaA, cheB, cheX, tsr and tar. The extent of methylation of the MCP is affected by the presence of attractants or repellents: addition of attractant increases the steady-state level of methylation; addition of repellent causes rapid demethylation to a new steady-state level. Methylation is inhibited by the addition of the transmethylase inhibitors A9145C and Sinefungin, which are S-adenosylmethionine analogs, and by S-adenosylhomocysteine.