The 86-kDa CABYR-A-only variant and CABYR-B-containing variants were co-immunoprecipitated with AKAP3 by anti-AKAP3 antibody. (a, b) 2D gels of human sperm extracts immunoprecipitated with anti-AKAP3 polyclonal antibody (a) and pre-immune serum (b) probed by the anti-CABYR-A polyclonal antibody. The spot indicated by an arrow (a) is the co-immunoprecipitated 86-kDa CABYR-A-only variant. (c, d) 2D gels of human sperm extracts immunoprecipitated with anti-AKAP3 polyclonal antibody (c) and pre-immune serum (d) probed by the anti-CABYR-B polyclonal antibody. The spot indicated by an arrow (c) is the co-immunoprecipitated CABYR-B-containing variant. AKAP, A kinase-anchoring protein; CABYR, calcium-binding tyrosine phosphorylation-regulated protein; MW, molecular weight; pI, isoelectric point.