The N-terminal domain of 'bypass of forespore C' is composed of a four-stranded beta-sheet covered by an alpha-helix. The beta-sheet has a beta2-beta1-beta4-beta3 topology, where strands beta1 and beta2 and strands beta3 and beta4 are connected by beta-turns, whereas strands beta2 and beta3 are joined by an alpha-helix that runs across one face of the beta-sheet. This domain is similar to the third immunoglobulin G-binding domain of protein G from Streptococcus, the latter belonging to a large and diverse group of cell surface-associated proteins that bind to immunoglobulins. It has been hypothesised that this domain may be a mediator of protein-protein interactions involved in proteolytic events at the cell surface [1].

1: The structure of bypass of forespore C, an intercompartmental signaling factor during sporulation in Bacillus. Patterson HM, Brannigan JA, Cutting SM, Wilson KS, Wilkinson AJ, Ab E, Diercks T, de Jong RN, Truffault V, Folkers GE, Kaptein R; J Biol Chem. 2005;280:36214-36220. PMID:16049010