Receptor methylesterase activity has also been ascribed to CheD in T.maritima[32].

Similar to the situation in E.coli[26, 106], receptor deamidase and methylesterase activities have been detected in Hbt.salinarum CheB [25]. It is not clear whether both CheB and CheD deamidate and/or demethylate receptors in the latter organism [25]. Thus the function of the CheD protein in Hbt.salinarum remains to be elucidated. We identified interactions between CheD and CheC2, CheC3, CheB, as well as CheF1, CheF2 and OE2401F. Hence CheD is a hub in the Hbt.salinarum Che protein interaction network. The high conservation of CheD among chemotactic bacteria and archaea [3] and the severe phenotype of a CheD deletion (almost complete loss click here of tactic capabilities; our unpublished results) support the hypothesis that this protein has a central role in the taxis signaling network. Of the interactions detected here, only CheC-CheD has been described before [29, 66]. In B.learn more subtilis an interaction of CheD with the MCPs was identified through Y2H analysis [113]. This interaction was not detected in the present study. This might be due to different functions of CheD in the two organisms. However, it seems more likely that the affinity of a putatively dynamic CheD-Htr interaction was simply CH5183284 concentration not high enough for detection

by our bait fishing methods. A CheD-dependent adaptation system in Hbt. salinarum? The interactors CheC and CheD in B.subtilis form a feedback loop from CheY-P to the transducers and thereby constitute one of the three adaptation systems of this organism (the other two being the methylation/demethylation system of CheR and CheB, and the CheV system) [48]. CheC binding to CheD decreases the latter’s receptor deamidase activity [30]. Additionally and more important for adaptation, CheD regulates the activity of CheA [113]. CheY-P stabilizes the CheC-CheD complex,

which in turn reduces CheA stimulation and thus closes the feedback circuit. Indeed, the CheY-P binding ability of CheC seems to be more important for B.subtilis chemotaxis than its enzymatic activity [30]. Morin Hydrate In contrast to B.subtilis, a direct regulation of CheA activity by CheD seems questionable in Hbt.salinarum since receptor deamidase or methylesterase activity in Hbt.salinarum have till now only been demonstrated for CheB and not for CheD [25]. Additionally, in Hbt.salinarum a CheY-dependent or CheY-P-dependent regulation of transducer demethylation was experimentally demonstrated by Perazzona and Spudich [114], which implies the presence of a slightly different adaptational mechanism. A predictive computational model of transducer methylation [47] strongly supports the possibility that in Hbt.salinarum CheY and not CheY-P is indeed the feedback regulator. Based on these findings we used the detected interactions to propose an alternative feedback mechanism from the response regulator to the Htrs that might contribute to adaptation.