FIG. 2.

Schematic representation of the conserved domains of the CbbRRS proteins based on the predictions from the protein families database of alignments (Pfam). CbbRR1 (response regulator 1) contains a REC domain followed by an HPt domain. CbbRR2 (response regulator 2) contains two distinct receiver domains (REC A and REC B). The hybrid sensor kinase CbbSR contains two transmembrane regions (TM), a large cytoplasmic sensor domain with two predicted PAS motifs, a kinase core with all the conserved catalytic boxes (N, G₁/D, F, and G₂), and a C-terminal receiver domain (REC).