Xenopus laevis egg jelly contains small proteins that are essential to fertilization

John H. Olson, Douglas E. Chandler

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

The eggs of Xenopus laevis are surrounded by investment layers of egg jelly that interact with the sperm immediately prior to fertilization. Components of these egg jelly layers are necessary for the fertilization of the egg by incoming sperm. Eggs which are stripped of their jelly layers are refractile to fertilization by sperm, but the addition of solubilized jelly promotes fertilization. We have shown previously that the egg jelly layers are composed of a fibrous network of glycoconjugates which loosely hold smaller diffusible components. Extracts of these diffusible components were prepared by incubation of freshly ovulated eggs in high-salt buffers for 12 h at 4°C. This diffusible component extract, when incubated with sperm, promoted the sperm's ability to fertilize dejellied eggs in a dose-dependent manner. In contrast, the high-molecular-weight 'structural' glycoconjugates of jelly that remain after extraction of the diffusible components did not increase fertilization efficiency of dejellied eggs nor did nonspecific proteins, carbohydrate polymers, or organic polymers. The diffusible components, analyzed by SDS-PAGE, consisted of a mixture of proteins from 4 to 180 kDa. The protein responsible for fertilization rescue appeared to be <50 kDa and appeared to self-aggregate or to bind to larger proteins. This protein component was required during sperm binding to the egg, its action required an intact egg vitelline envelope, and its action was independent of large soluble polymers such as Ficoll.

Original languageEnglish (US)
Pages (from-to)401-410
Number of pages10
JournalDevelopmental Biology
Volume210
Issue number2
DOIs
StatePublished - Jun 15 1999

Keywords

  • Egg jelly
  • Fertilization
  • Sperm-egg interaction
  • Xenopus laevis

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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