Figure 1
The structures of the components of the photosensory system of H. salinarum. The figure shows the structures of the components of the receptor-transducer-CheW-CheA (R-TWA) complex (stoichiometry SRI:HtrI:CheW:CheA = 2:2:2:2) and of CheY, CheB, and CheR. The membrane embedded light-receptor SRI (orange) interacts with the membrane embedded transducer HtrI (green) and the signaling state is transferred to the histidine kinase CheA (blue) which is bound via the scaffold protein CheW (brown) to the signaling domain of HtrI. An active signaling state of HtrI enhances autophosphorylation of CheA, and the phosphate group is then transferred to the response regulator CheY (purple). The methyl-transferase CheR (red; +CH3) and the methyl-esterase CheB (yellow; -CH3) bring about adaptation by reversible methylation. Protein structures were obtained by homology modeling and the arrangement of the quaternary structure is based on the spatial organization of the Escherichia coli chemotaxis system proposed by [77, 78] and of the SRII and HtrII interaction in the archeaon Natronomonas pharaonis [29]. The arrangement is not meant to imply that the domains or proteins are oriented or contact each other in the depicted manner.