FIG. 1.
Domain organization of the protein constructs used in the present study. Full-length WalKSpn (VicK) (line 1) contains 449 amino acids organized into five architectural and functional domains based on the SMART database (smart.embl-heidelberg.de): TM (anchoring transmembrane domain; amino acids 13 to 32), HAMP linker domain (amino acids 16 to 84), PAS domain consisting of PAS and PAC motifs (amino acids 94 to 202), DHp (dimerization histidine phosphoryltransfer [HisKA]; amino acids 208 to 274), and CA (kinase catalytic domain [HATPase]; amino acids 323 to 435). Histidine residue 218 (H218) is phosphorylated in the autokinase reaction. Numbering of full-length WalKSpn was extended to the soluble, truncated WalKSpn derivatives purified and characterized in the present study (lines 2 to 10; Materials and Methods; see Fig. S1 in the supplemental material). The affinity tags on the constructs are indicated. Full-length WalRSpn (VicR) contains 234 amino acids organized into two domains: a receiver domain (amino acids 2 to 112) and an effector domain (amino acids 154 to 230). Aspartate residue 52 in the receiver domain is phosphorylated in the transferase reaction with WalKSpn∼P constructs, and the effector domain contains the helix-turn-helix DNA binding motif. See the text for further details.