This family represents a conserved region approximately 350 residues long within the selenoprotein B component of the bacterial glycine, sarcosine and betaine reductase complexes.

1: Purification and characterization of protein PB of betaine reductase and its relationship to the corresponding proteins glycine reductase and sarcosine reductase from Eubacterium acidaminophilum. Meyer M, Granderath K, Andreesen JR; Eur J Biochem 1995;234:184-191. PMID:8529639