The carboxy-terminal portion of the CheA kinase mediates regulation of autophosphorylation by transducer and CheW

Abstract

The CheA kinase is a central protein in the signal transduction network that controls chemotaxis in Escherichia coli. CheA receives information from a transmembrane receptor (e.g., Tar) and CheW proteins and relays it to the CheB and CheY proteins. The biochemical activities of CheA proteins truncated at various distances from the carboxy terminus were examined. The carboxy-terminal portion of CheA regulates autophosphorylation in response to environmental signals transmitted through Tar and CheW. The central portion of CheA is required for autophosphorylation and is also presumably involved in dimer formation. The amino-terminal portion of CheA was previously shown to contain the site of autophosphorylation and to be able to transfer the phosphoryl group to CheB and CheY. These studies further delineate three functional domains of the CheA protein.

Characterization of the chemotaxis protein CheW from Rhodobacter sphaeroides and its effect on the behaviour of Escherichia coli

“…Little is known about the role of cheW in any chemotactic bacteria. In E. coli, cheW is an essential requirement of MCP-dependent chemotaxis (Conley et al, 1989) and has been shown to interact with the signalling domain of Tsr and the carboxy-terminus of CheA, suggesting a role as a linker protein between the sensor (MCP) and the HPK (CheA) (Gegner and Dahlquist, 1991;Liu and Parkinson, 1991;Bourret et al, 1993). No catalytic activity has been attributed to CheW, although Sanders et al (Sanders et al, 1989) have shown that overexpression of CheW produces a phenotype identical to its deletion, suggesting that CheW binds and locks the MCPs and/or CheA in an inactive conformation.…”

Active Site Interference and Asymmetric Activation in the Chemotaxis Protein Histidine Kinase CheA

“…The H and Y domains are attached to one another and to the C domain by flexible linker sequences, and it is apparent that the two globular domains are free to move in solution like balls on a chain. No structural information is available concerning the C and R domains, although it has been shown that the R domain can be cleaved away without dramatically affecting the activity of the CheA catalytic domain (8).…”

Chemotaxis in Rhodobacter sphaeroides Requires an Atypical Histidine Protein Kinase

“…CheB-P is a methylesterase that demethylates methylated glutamate residues on the chemoreceptors and promotes adaptation to the current environmental conditions (10). E. coli CheA has five domains: P1 is a histidine phosphotransferase (Hpt) 1 domain that contains the conserved phosphorylatable histidine residue (11); P2 binds the response regulators and, although it is not essential for phosphotransfer from the P1 domain to the response regulators, it does accelerate the process (12,13); P3 is the dimerization domain; P4 is the kinase domain that binds ATP and phosphorylates the P1 domain; it is characterized by the conserved N, G1, F, and G2 sequence boxes (11); and P5 is the regulatory domain that interacts with CheW and the chemoreceptors (14). In this report we will call proteins with an identical domain organization to E. coli classic CheAs, whereas chemotaxis proteins containing at least two of the E. coli CheA domains but either lacking some of the other domains or containing additional domains are called atypical CheAs.…”