Synonyms:CABYR, Calcium binding protein 86, Cancer/testis antigen 88, CBP86, CT88, Fibrousheathin 2, Fibrousheathin II, FSP 2, FSP2 Background:May function as a regulator of both motility-and head-associated functions such as capacitation and the acrosome reaction. Isoform 1 binds calcium in vitro. Isoform 2 and isoform 6 probably bind calcium. Isoform 3 and isoform 5 do not bind calcium in vitro. Isoform 4 probably does not bind calcium.