Homocysteine biosynthesis enzyme, sulfur-incorporation (IPR002708)

Short name: HcyBio

Overlapping homologous superfamilies


Domain relationships



This presumed domain is about is about 360 residues long. The function of this domain is unknown. It is found in some proteins that have two C-terminal CBS domains. There are also proteins that contain two inserted Fe4S domains near the C-terminal end of the domain. The protein O26943 has been misannotated as an inosine monophosphate dehydrogenase based on the similarity to the CBS domains. Based on genetic analyses in the methanogen Methanosarcina acetivorans, this family is a key component of the metabolic network for sulfide assimilation and trafficking in methanogens. It is essential to a novel, O-acetylhomoserine sulfhydrylase-independent pathway for homocysteine biosynthesis, and may catalyse sulfur incorporation into the side chain of an as yet unidentified amino acid precursor [PMID: 25315403]. The DUF39-CBS and DUF39-ferredoxin architectures repeatedly occur together in the genomes of methanogenic Archaea, suggesting they may be of diverged function. This is consistent with a phylogenetic reconstruction of the DUF39 family, which clearly distinguishes the CBS-associated and ferredoxin-associated DUF39s [PMID: 25315403].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.