This domain is found at the N terminal of Swiss:Q9Y6R7 and has been shown to confer IgG Fc binding activity [1]. It may play a role in immune protection and inflammation in the intestines of primates [1].

1: Human IgGFc binding protein (FcgammaBP) in colonic epithelial cells exhibits mucin-like structure. Harada N, Iijima S, Kobayashi K, Yoshida T, Brown WR, Hibi T, Oshima A, Morikawa M; J Biol Chem. 1997;272:15232-15241. PMID:9182547