InterPro: IPR017678 CoB--CoM heterodisulphide reductase, subunit B

This entry represents subunit B (HdrB) from CoB--CoM heterodisulphide reductase (or heterodisulphide reductase; Hdr; EC:1.8.98.1), an iron-sulphur protein found in methanogenic archaea [1]. Hdr catalyses the reversible reduction of the heterodisulphide (CoM-S-S-CoB) to the thiol-coenzymes: coenzyme M (H-S-CoM) and coenzyme B (H-S-CoB). Hdr is composed of three subunits: hdrA (subunit A), hdrB (subunit B) and hdrC (subunit C). Hdr forms a complex with the F420-non-reducing hydrogenase (Mvh), which provides the reducing equivalents to the heterodisulphide reductase.

All processes in methanogenesis lead to the formation of a mixed disulphide bond between coenzyme-M and coenzyme-B, by a reaction in which coenzyme B reduces methyl-CoM, leading to formation of methane and a CoB-CoM heterodisulphide [2]. There are two different systems that are capable of reducing the CoB-CoM heterodisulphide, using either H2 or a reduced cofactor F420 as electron donors [3].

HdrB may have a function in energy transduction. Some archaea species have two copies, HdrB1 and HdrB2.