InterPro: IPR008924 Methyl-coenzyme M reductase, alpha/beta subunit, C-terminal

Methyl-coenzyme M reductase (MCR) catalyses the reduction of methyl-coenzyme M (CH3-SCoM) and coenzyme B (HS-CoB) to methane and the corresponding heterosulphide CoM-S-S-CoB (EC:2.8.4.1), the final step in methane biosynthesis. This reaction proceeds under anaerobic conditions by methanogenic Archaea [1], and requires a nickel-porphinoid prosthetic group, coenzyme F430, which is in the EPR-detectable Ni(I) oxidation state in the active enzyme. Studies on a catalytically inactive enzyme aerobically co-crystallized with coenzyme M displayed a fully occupied coenzyme M-binding site with no alternate conformations. The binding of coenzyme M appears to induce specific conformational changes that suggests a molecular mechanism by which the enzyme ensures that methyl-coenzyme M enters the substrate channel prior to coenzyme B, as required by the active-site geometry [2].

MCR is a hexamer composed of 2 alpha, 2 beta, and 2 gamma subunits with two identical nickel porphinoid active sites, which form two long active site channels with F430 embedded at the bottom [3, 4].

This entry represents the C-terminal domain of the alpha and beta subunits, which share a common structure. The C-terminal domain is a multi-helical bundle and contains a buried central helix.