TY - JOUR
T1 - Xenopus laevis egg jelly contains small proteins that are essential to fertilization
AU - Olson, John H.
AU - Chandler, Douglas E.
N1 - Funding Information:
The authors thank Dr. Allan Bieber for technical and experimental advice on numerous occasions. We also acknowledge the technical assistance of James Ridgway and Rodrigo Reyes. Part of this work was carried out in the W. M. Keck Bioimaging Laboratory established by the W. M. Keck Foundation. This work was supported by Grant IBN-9807862 from the National Science Foundation and by a Research Incentive Award from Arizona State University.
PY - 1999/6/15
Y1 - 1999/6/15
N2 - 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.
AB - 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.
KW - Egg jelly
KW - Fertilization
KW - Sperm-egg interaction
KW - Xenopus laevis
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U2 - 10.1006/dbio.1999.9281
DO - 10.1006/dbio.1999.9281
M3 - Article
C2 - 10357899
AN - SCOPUS:0033564463
SN - 0012-1606
VL - 210
SP - 401
EP - 410
JO - Developmental Biology
JF - Developmental Biology
IS - 2
ER -