Reticulocalbin 3, also known as RCN3, is a member of the CREC (cab45/reticulocalbin/ ERC45/calumenin) family. RCN3 contains five Arg-Xaa-Xaa-Arg motifs, which function as target sequences of SPCs (subtilisin-like proprotein convertases), a family of serine endoproteases that proteolytically activate proproteins. The synthesis of one such member, PACE4 (paired basic amino acid cleaving enzyme 4), is influenced by association and coexpression with reticulocalbin-3.