Members of this family include benzylsuccinate synthase beta subunit found in bacteria. BssB acts as a regulator of activation and may additionally be involved in regulating access to the enzyme's active site. It adopts a fold similar to that of a high potential iron-sulfur protein (HiPIP) and resembles the single small subunit of HPAD, which is known as the HpdC or HPADgamma in that system [1].

1: Structures of benzylsuccinate synthase elucidate roles of accessory subunits in glycyl radical enzyme activation and activity. Funk MA, Judd ET, Marsh EN, Elliott SJ, Drennan CL; Proc Natl Acad Sci U S A. 2014;111:10161-10166. PMID:24982148