Characterization of anti-sticking factor-II from goat epididymal plasma

A previous study has characterized the major 47 kDa anti-sticking factor (ASF-I) from goat cauda-epididymal plasma (Roy, N., and Majumder, G.C., Biochim. Biophys. Acta, 991:114-122, 1989). This study reports the purification and characterization of ASF-II, another anti-sticking factor from the goat epididymal plasma. ASF-II was purified to apparent homogeneity by using concanavalin A-agarose affinity chromatography, DEAE-cellulose chromatography, alumina gel adsorption, and isoelectric focussing techniques. It showed a single protein band by both non-denaturing and SDS-polyacrylamide gel electrophoresis. ASF-II showed a molecular weight of 36,000 and a sedimentation constant of 2.4S. ASF-II is largely stable to heat treatment and it is a specific glycoprotein having high affinity and specificity for its anti-sticking action. At saturating concentration (1 nM) it inhibited adhesion of nearly 50% of spermatozoa to the glass surface of the haemocytometer counting chamber. Both the protein and sugar parts of the factor are essential for the anti-sticking activity since it lost its activity completely when treated with trypsin, L-fucosidase, or mannosidase. ASF-II does not coat the glass surface and it binds to spermatozoa. Data are consistent with the view that ASF-II has not been derived from the larger ASF-I molecule due to its enzymic modifications. Both ASF-I and -II had no effect on sperm forward motility as evidenced by spectrophotometric motility assays, indicating thereby the suitability of the factors to improve the existing sperm motility assays by eliminating the possibility of cell-sticking artifacts.