This domain is found in various molybdopterin - containing oxidoreductases and tungsten formylmethanofuran dehydrogenase subunit d (FwdD) and molybdenum formylmethanofuran dehydrogenase subunit (FmdD); where the domain constitutes almost the entire subunit. The formylmethanofuran dehydrogenase catalyses the first step in methane formation from CO2 in methanogenic archaea and has a molybdopterin dinucleotide cofactor [1]. This domain corresponds to the C-terminal domain IV in dimethyl sulfoxide (DMSO)reductase which interacts with the 2-amino pyrimidone ring of both molybdopterin guanine dinucleotide molecules [2].

1: The formylmethanofuran dehydrogenase isoenzymes in Methanobacterium wolfei and Methanobacterium thermoautotrophicum: induction of the molybdenum isoenzyme by molybdate and constitutive synthesis of the tungsten isoenzyme. Hochheimer A, Hedderich R, Thauer RK; Arch Microbiol 1998;170:389-393. PMID:9818358

2: Crystal structure of dimethyl sulfoxide reductase from Rhodobacter capsulatus at 1.88 A resolution. Schneider F, Lowe J, Huber R, Schindelin H, Kisker C, Knablein J; J Mol Biol 1996;263:53-69. PMID:8890912