Functional homology of chemotactic methylesterases from Bacillus subtilis and Escherichia coli.

The methylesterase enzyme from Bacillus subtilis was compared with that from Escherichia coli. Both enzymes were able to demethylate methyl-accepting chemotaxis proteins (MCPs) from the other organism and were similarly affected by variations in glycerol, magnesium ion, or pH. When attractants were added to a mixture of B. subtilis MCPs and E. coli methylesterase, the rate of demethylation was enhanced. Conversely, when attractants were added to a mixture of E. coli MCPs and B. subtilis methylesterase, the rate of demethylation was diminished. These effects are what would be expected if, in these in vitro systems, the MCPs determined the rate of demethylation. These data suggest that, although the enzymes are from evolutionarily divergent organisms and are different in size, they have considerable functional homology.