Calcium-binding tyrosine phosphorylation-regulated protein
Cancer/testis antigen 88
Testis-specific calcium-binding protein CBP86
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.
Expressed in elongating spermatids and spermatozoa (at protein level). Isoform 1 is expressed in testis. Isoform 3 and isoform 5 are also expressed in brain, pancreas and numerous brain tumors.
Contains 1 RIIa domain.
Isoform 1 is phosphorylated on tyrosine residues during in vitro capacitation. Isoform 3 and isoform 5 are phosphorylated by GSK3B in vitro. Dephosphorylation affects its ability to bind calcium.
Cytoplasm > cytoskeleton. Cell projection > cilium > flagellum. Localized to fibrous sheath including the surface of the longitudinal columns and ribs of the principal piece of sperm flagella and Nucleus. Cytoplasm. Cell projection > cilium > flagellum. According to PubMed:15752768, isoform 1, isoform 3 and isoform 5 are both nuclear and cytoplasmic.