| Type: | Domain | Name: | Sirohaem synthase, dimerisation domain |
| Description: | Bacterial sulphur metabolism depends on the iron-containing porphinoid sirohaem. CysG is a multi-functional enzyme with S-adenosyl-L-methionine (SAM)-dependent bismethyltransferase, dehydrogenase and ferrochelatase activities. CysG synthesizes sirohaem from uroporphyrinogen III via reactions which encompass two branchpoint intermediates in tetrapyrrole biosynthesis, diverting flux first from protoporphyrin IX biosynthesis and then from cobalamin (vitamin B12) biosynthesis. CysG is a dimer. Its dimerisation region is 74 residues long, and acts to hold the two structurally similar protomers held together asymmetrically through a number of salt-bridges across complementary residues within the dimerisation region []. CysG dimerisation produces a series of active sites, accounting for CysG's multi-functionality, catalysing four diverse reactions:Two SAM-dependent methylationsNAD+-dependent tetrapyrrole dehydrogenationMetal chelation | Short Name: | Sirohaem_synthase_dimer_dom |
