Phosphotransfer in XXXX chemotaxis.

@entity49205 @entity11704 @entity3793 @entity526 @entity855 @entity16258
The two-component sensing system controlling bacterial chemotaxis is one of the best studied in biology. @entity11704 has a complex chemosensory pathway comprising two @entity3793 protein kinases (CheAs) and eight downstream response regulators (six CheYs and two CheBs) rather than the single copies of each as in @entity526 . We used in vitro analysis of phosphotransfer to start to determine why @entity11704 has these multiple homologues. CheA(1) and CheA(2) contain all the key motifs identified in the @entity3793 protein kinase family, except for conservative substitutions (F-L and F-I) within the F box of CheA(2), and both are capable of @entity855 -dependent autophosphorylation. While the K(m) values for @entity855 of CheA(1) and CheA(2) were similar to that of @entity526 , the k(cat) value was three times lower, but similar to that measured for the related @entity16258 CheA. However, the two CheAs differed both in their ability to phosphorylate the various response regulators and the rates of phosphotransfer. CheA(2) phosphorylated all of the CheYs and both CheBs, whilst CheA(1) did not phosphorylate either @entity49205 and phosphorylated only the response regulators encoded within its own genetic locus (CheY(1), CheY(2), and CheY(5)) and CheY(3). The dephosphorylation rates of the @entity11704 CheBs were much slower than the @entity526 CheB. The dephosphorylation rate of CheY(6), encoded by the third chemosensory locus, was ten times faster than that of the @entity526 CheY. However, the dephosphorylation rates of the remaining @entity11704 CheYs were comparable to that of @entity526 CheY.
