Structural domains comprising this superfamily share the structure of the N-terminal domain of the 'bypass of forespore C' (BofC) protein, which acts negatively on inter-compartmental signalling of pro-sigma(K) processing in the sigma(K)-checkpoint of Bacillus subtilis. This is achieved through its interaction with SpoIV inhibiting autoproteolysis of the latter which leads to a delay in proteolytic cleavage of pro-sigma(K) PMID:10931291.

BofC is a monomer made up of two domains, an N-terminal and a C-terminal domain. The N-terminal domain is structurally related to the third immunoglobulin-binding domain of protein G from Streptococcus. By analogy with protein G, it has been suggested that this N-terminal domain of BofC mediates protein-protein interactions.PMID:16049010.