Class III adenylyl cyclases usually possess six highly conserved catalytic residues. Deviations in these canonical amino acids are observed in several putative adenylyl cyclase genes as apparent in several bacterial genomes. This suggests that a variety of catalytic mechanisms may actually exist. The geneRv0386from Mycobacterium tuberculosiscodes for an adenylyl cyclase catalytic domain fused to an AAA-ATPase and a helix-turn-helix DNA-binding domain.