This family consist of methyl-viologen-reducing hydrogenase, delta subunit / heterodisulphide reductase. No specific functions have been assigned to this subunit. The aligned region corresponds to almost the entire delta chain sequence and contains 4 conserved cysteine residues. However, in two Archaeoglobus sequences this region corresponds to only the C-terminus of these proteins Swiss:O29030 and Swiss:029595.

1: Organization and growth phase-dependent transcription of methane genes in two regions of the Methanobacterium thermoautotrophicum genome. Nolling J, Pihl TD, Vriesema A, Reeve JN; J Bacteriol 1995;177:2460-2468. PMID:7730278