Studies on bacterial chemotaxis. V. Possible involvement of four species of the methyl-accepting chemotaxis protein in chemotaxis of Escherichia coli.

Chemotactic Escherichia coli contains five major methyl-accepting proteins. Three of them were identified as the product of tsr gene, tar gene and peptide elongation factor Tu. Electrophoretic analysis of sulfur-labeled proteins and methyl-labeled proteins from trg mutants, which lost the ability of chemotaxis only towards ribose, galactose and their analogs, showed that the product of trg gene was another methyl-accepting protein i.e. a methyl-accepting chemotaxis protein for ribose and galactose (trg-MCP). The last methylatable protein, named as MCP-IV, seems to be involved in chemosensory transduction (accompanying paper). Thus, it is possible that chemosensory transduction in E. coli involves four species of MCP, although no genetic evidence for MCP-IV has yet been found. A hypothesis relating a change in the methylation of MCP with a movement of ions is presented.