ニワトリ卵巣での卵成熟に伴う卵黄膜内層タンパク質の変化

Abstract

To clarify the formation of the vitelline membrane, we investigated changes in the proteins constituting the inner layer of the vitelline membrane during the ovum maturation in the hen ovary.The vitelline membranes were isolated from yellow yolk follicles at the different growth stages, identified as F_1 to F_8,and their protein compositions were examined by SDS-PAGE in both the presence and the absence of reducing agent. One of the major glycoproteins found in the matured ovum, GP-I, appears to exist as monomer from the early stage of the yolk deposition (F_1). The other glycoprotein, GP-II, appears as protomer of its precursor with higher molecular weight at slightly later stage (F_3) and appears to be converted into the homodimeric form at later stages (F_7～F_8). Staining the gel for the carbohydrate moiety supports this notion. The GP-I fraction prepared from the vitelline membrane of the completed eggs was separated into two components, GP-Ia and GP- Ib, based on the pH dependence in their solubility. They have similar molecular weights but different elution volumes in cation-exchange chromatography. A similar but different heterogeneity in the GP- I fraction prepared from the follicle vitelline membrane was identified.These results indicate that proteins constituting the vitelline membrane, at least GP-I and GP-II, are processed to a great extent during the ovum maturation as well as after the ovulation.