Experiments have been carried out to identify
proteins on boar spermatozoa that bind to components of the zona pellucida.
Polypeptides in
sodium deoxycholate extracts of boar spermatozoa and in whole seminal plasma have been separated by
sodium dodecyl sulphate-
polyacrylamide gel electrophoresis, transferred onto
nitrocellulose sheet by electroblotting and probed with 125I-labelled heat-solubilized zona pellucida from pig oocytes or ovulated eggs.
Zona proteins bound avidly and consistently to a
polypeptide of Mr 53,000 on blots of capacitated and noncapacitated sperm and weakly to
polypeptides of Mr 67,000, 38,000 and 18,000. On blots of seminal plasma the 125I-labelled probes bound to two
polypeptides of Mr 65,000 and 19-24,000. Identification of the
zona proteins that were binding to the aforementioned
proteins on blots showed that all the major
zona pellucida glycoproteins were involved, including those acquired from oviduct secretions. Binding of 125I-ovulated zona pellucida to the
polypeptide of Mr 53,000 also occurred in extracts of testicular and epididymal boar spermatozoa. The results are discussed in relation to sperm-egg recognition in the pig.