Characterization of Porcine Oocyte Zonae Pellucidae by Polyacrylamide Gel Electrophoresis

Abstract

Polyacrylamide gel electrophoresis of zonae pellucidae isolated from porcine ovarian oocytes and dissolved in either 6 M urea or 2.0% SDS suggest that the zona pellucida is composed of a single protein in addition to a carbohydrate component. The structural organization of the protein in the porcine zona pellucida is postulated to consist of repeating units of this single protein maintained by noncovalent bonding. Electrophoresis in SDS-.beta.-MSH [sodium dodecyl sulfate-.beta.-mercaptoethanol] polyacrylamide gels has shown the protein to be composed of 4 polypeptide or protein subunits with molecular weights of 17,000 D [density], 57,000 D, 66,000 D and 85,000 D. The proteins may be cross-linked by disulfide bridges comprising the single protein visualized in gels without .beta.-MSH. The subunit proteins may be in a multimeric arrangement supported by covalent bonds which maintain the complex structure. Relative percentages of the subunit proteins determined by scanning densitometry were: 50.3% (17,000 D), 23.7% (57,000 D), 18.6% (66,000 D) and 6.% (85,000 D). The unequal percentages reported by densitometry may indicate the number of molecular subunit species within a complex.