InterPro : IPR006367

Name  Sirohaem synthase, N-terminal Short Name  Sirohaem_synthase_N
Type  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 chelationThis group represent a subfamily of CysG N-terminal region-related sequences. All sequences in the seed alignment for this model are N-terminal regions of known or predicted sirohaem synthases. The C-terminal region of each is uroporphyrin-III C-methyltransferase (), which catalyses the first step committed to the biosynthesis of either sirohaem or cobalamin (vitamin B12) rather than protohaem (haem). Functionally these sequences complete the process of oxidation and iron insertion to yield sirohaem. Sirohaem is a cofactor for nitrite and sulphite reductases, so sirohaem synthase is CysG of cysteine biosynthesis in some organisms.

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

1 Contains

Id Name Short Name Type
IPR019478 Sirohaem synthase, dimerisation domain Sirohaem_synthase_dimer_dom Domain

2 Found In

Id Name Short Name Type
IPR012066 Uroporphyrin-III C-methyltransferase, yeast SUMT_yeast Family
IPR012409 Sirohaem synthase Sirohaem_synth Family

1 Parent Features

Id Name Short Name Type
IPR016040 NAD(P)-binding domain NAD(P)-bd_dom Domain

1 Publications

First Author Title Year Journal Volume Pages
Stroupe ME CysG structure reveals tetrapyrrole-binding features and novel regulation of siroheme biosynthesis. 2003 Nat Struct Biol 10 1064-73

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)