RUI: Glycosidase Release and the Block to Polyspermy in Ascidian Eggs

兰伯特博士和古德博士将研究阻止海鞘卵多精的方法。根据他们的模型，精子与卵子卵黄膜上的糖苷结合。结合在卵磷脂外壳上的精子数量增加之后会迅速减少。这种结合的减少有助于确保只有一个精子进入卵子。精子结合被Na+依赖的糖苷酶的释放所抑制，该酶修饰卵磷脂外壳精子受体。他们假设糖苷酶最初与卵膜相连，并在受精时迅速排出。事实上，洗涤剂和磷脂酶C可以将酶从未受精卵中释放出来，这表明酶与膜磷脂有关。他们的模型包括糖苷酶与磷脂酰胆碱的连接，以及导致酶释放的磷脂酶的Na+依赖性激活。糖苷酶和磷脂酶将被分离并广泛表征。制备两种蛋白的抗体用于超微结构酶定位。通过使用磷脂酶激动剂和拮抗剂以及通过直接测量未受精卵和受精卵的磷脂酶活性来探索其释放机制。G蛋白和G离子在海鞘卵活化中的作用也将被探讨。虽然每个卵子产生数百万个精子，但如果超过一个精子进入卵子，卵裂就会严重异常，死亡是不可避免的。因此，阻止额外精子的进入对生育能力至关重要。兰伯特博士和古德博士将通过研究精子进入和阻断海鞘系统的分子细节来进一步了解这一现象。

Dr.Lambert and Dr.Goode will study a block to polyspermy in the Ascidian egg. According to their model, the sperm bind to glycosides on the vitelline coat of the egg. An increase in the number of sperm binding to the vitelline coat is followed by a rapid decline. This decline in binding helps insure that only a single sperm enters the egg. Sperm binding is inhibited by the Na+-dependent release of a glycosidase that modifies the vitelline coat sperm receptors. They hypothesize that the glycosidase is initially linked to the egg membrane and is rapidly discharged at fertilization. The fact that detergents and Phospholipase C can free the enzyme from the unfertilized egg suggest that the enzyme is linked to a membrane phospholipid. Their model includes linkage of the glycosidase to a phosphatidylcholine and the Na+-dependent activation of a phospholipase that causes enzyme release. The glycosidase and phospholipase will be isolated and extensively characterized. Antibodies will be prepared to both proteins for ultrastructural enzyme localization. The mechanism of release will be probed through the use of phospholipase agonists and antagonists and also through the direct measurement of phospholipase activity in unfertilized and fertilized eggs. The role of G proteins and ions in Ascidian egg activation will also be probed. %%% Although millions of sperm are produced for each egg, if more than a single sperm enters the egg,cleavage is grossly abnormal and death is inevitable. As a consequence, blocking the entry of additional sperm is of critical importance to fertility. Dr.Lambert and Dr. Goode will further the understanding of this phenomenon by studying the molecular details of sperm entry and blocking in the Ascidian system.