SPERM MOTILITY INITIATION-FACTOR IS A MINOR COMPONENT OF THE PACIFIC HERRING EGG CHORION

Polyclonal antibodies were generated to the 105 kDa herring sperm moti lity initiation factor (SMIF) and used to explore the role of SMIF in sperm-egg interaction. Using sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting with SMIF antibodies, it was demon strated that SMIF is present as a minor (4-7% of total chorion protein ) component of the chorion. The major polypeptides in the chorion migr ated at 117 kDa and in a grouping between 48-54 kDa, with other minor bands above and below. The only detectable glycosylated component was the 105 kDa band, which was resolved at two isoelectric points (8.22 a nd 8.31) after isoelectric focusing gel electrophoresis. Using antibod ies to SMIF, fertilization was blocked, sperm motility was inhibited i n vitro in the presence of solubilized SMIF and SMIF binding sites on sperm were localized. Lastly, SMIF was localized to the region of the herring egg that encircles the micropyle.