Alignment of the TK sequence of VKR proteins using the CLUSTALW algorithm. Numbers I to XI correspond to the eleven subdomains conserved in protein kinase domains. Essential motifs for protein kinase activity are indicated in red. The motif G8xGxxGxV15 is required for binding of ATP and V32AxK (16×)E52 for its stabilization. The motif H147RD(L/V/I)xxRNxL156 is implicated in phosphotransfer and the triplet D194FG196 is the Mg2+ binding site. The two residues Y211 and Y212 constitute the autophosphorylation site and the motif M262(A/S)PE265 is required for stabilization of the active kinase core.