CheY-dependent methylation of the asparagine receptor, McpB, during chemotaxis in Bacillus subtilis

For the Gram-positive organism Bacillus subtilis, chemotaxis to the attract ant asparagine is mediated by the chemoreceptor McpB. In this study, we sho w that rapid net demethylation of B. subtilis McpB results in the immediate production of methanol, presumably due to the action of CheB. We also show that net demethylation of McpB occurs upon both addition and removal of as paragine. After each demethylation event, McpB is remethylated to nearly pr estimulus levels. Both remethylation events are attributable to CheR using S-adenosylmethionine as a substrate. Therefore, no methyl transfer to an in termediate carrier need be postulated to occur during chemotaxis in B. subt ilis as was previously suggested. Furthermore, we show that the remethylati on of asparagine-bound McpB requires the response regulator, CheY-P, sugges ting that CheY-P acts in a feedback mechanism to facilitate adaptation to p ositive stimuli during chemotaxis in B. subtilis, This hypothesis is suppor ted by two observations: a cheRBCD mutant is capable of transient excitatio n and subsequent oscillations that bring the flagellar rotational bias belo w the prestimulus value in the tethered cell assay, and the cheRBCD mutant is capable of swarming in a Tryptone swarm plate.