Evidence for the Involvement of Zinc in the Association of CRISP1 with Rat Sperm During Epididymal Maturation

Rat epididymal protein CRISP1 (cysteine-rich secretory protein 1) associates with sperm during maturation and participates in fertilization. Evidence indicates the existence of two populations of CRISP1 in sperm: one loosely bound and released during capacitation, and one strongly bound that remains after this process. However, the mechanisms underlying CRISP1 binding to sperm remain mostly unknown. Considering the high concentrations of Zn2+ present in the epididymis, we investigated the potential involvement of this cation in the association of CRISP1 with sperm. Caput sperm were coincubated with epididymal fluid in the presence or absence of Zn2+, and binding of CRISP1 to sperm was examined by Western blot analysis. An increase in CRISP1 was detected in sperm exposed to Zn2+, but not if the cation was added with ethylenediaminetetra-acetic acid (EDTA). The same results were obtained using purified CRISP1. Association of CRISP1 with sperm was dependent on epididymal fluid and Zn2+ concentrations and inc...