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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",