CheR- and CheB-dependent chemosensory adaptation system of XXXX .

@entity11704 @entity1042 @entity5498 @entity3881 @entity526
@entity11704 has multiple homologues of most of the @entity526 chemotaxis genes, organized in three major operons and other, unlinked, loci. These include cheA(1) and cheR(1) (che Op(1)) and cheA(2), cheR(2), and cheB(1) (che Op(2)). In-frame deletions of these cheR and cheB homologues were constructed and the chemosensory behaviour of the resultant mutants examined on swarm plates and in tethered cell assays. Under the conditions tested, CheR(2) and CheB(1) were essential for normal chemotaxis, whereas CheR(1) was not. cheR(2) and cheB(1), but not cheR(1), were also able to complement the equivalent @entity526 mutants. However, none of the proteins were required for the correct polar localization of the chemoreceptor McpG in @entity11704 . In @entity526 , CheR binds to the NWETF motif on the high-abundance receptors, allowing methylation of both high- and low-abundance receptors. This motif is not contained on any @entity11704 chemoreceptors thus far identified, although 2 of the 13 putative chemoreceptors, McpA and TlpT, do have similar sequences. This suggests that CheR(2) either interacts with the NWETF motif of @entity526 @entity5498 -accepting chemotaxis proteins (MCPs), even though its native motif may be slightly different, or with another conserved region of the MCPs. @entity1042 release measurements show that @entity11704 has an adaptation system that is different from that of @entity3881 and @entity526 , with @entity1042 release measurable on the addition of attractant but not on its removal. Intriguingly, CheA(2), but not CheA(1), is able to phosphorylate CheB(1), suggesting that signaling through CheA(1) cannot initiate feedback receptor adaptation via CheB(1)-P.
