鲍配子识别蛋白的研究

The Research Progress of Abalone's Gamete Recognition Protein

配子相互作用的生化机制对于进一步阐明生殖过程具有重要作用 ,它是深入了解细胞内识别的理想体系。精卵细胞相互作用包括一系列的步骤 ,开始于精子与卵细胞外被的接触 ,终止于两性细胞的融合及精子核进入卵细胞质中 ,而精卵细胞的识别具有建立于各自性细胞表面成分基础上的种的特异性 ,鲍则是研究精卵识别的好材料。鲍精子在发生顶体反应时释放出两种蛋白质———细胞溶素 (lysin)和 1 8ku糖蛋白 (sp1 8) ,其中的细胞溶素与其卵黄膜上的受体紧密结合 ,并利用非酶反应在卵黄膜上穿一个小孔 ,整个精子则从此孔穿过卵黄膜与卵细胞融合 ;sp1 8释放后则覆盖到精子细胞膜表面 ,起到溶解卵细胞脂质体的作用 ,即sp1 8介导精、卵细胞膜的融合。鲍卵细胞膜上存在细胞溶素受体 ,它是大的不分支的糖蛋白分子 ,占据了卵黄膜 3 0 %的组分 ,可以专一性地与细胞溶素相结合。这些配子识别蛋白共同进化且速度很快 ,其中细胞溶素和 1 8ku糖蛋白通过正向选择进化 ,而细胞溶素受体进行协同进化。

Study on the biochemical mechanism of gamete interaction is important for further understanding of the fertilization process,and also because it represents an ideal system to learn more about inter-cellular recognition. Sperm-egg interaction involves a series of steps that begin from the contact of sperm with the envelope of the egg, and end with the fusion of the two gametes and incorporation of the sperm nuclear in the egg cytoplasm. Such interaction is species-specific based on molecular recognition between gamete surface components. Abalone is the better animal for studying gamete recognition. During acrosomal process the lysin and sp18 are released,and lysin binds tightly to the VE receptor for lysin (VERL) and creates a hole in the egg vitelline envelope (VE) by a nonenzymatic mechanism. Through this hole the sperm passes the VE and fuses with egg. Sp18 is an 18 ku protein that coats the sperm surface during acrosomal process to mediate fusion between sperm and egg cell membranes. The VERL, a giant, unbranched glycoprotein comprising 30% of the VE, exists in the vitelline envelope and fuses with lysin by species-specificity. These recognition proteins coevolved with high speed,but VERL with concerted evolution and lysin and sp18 with positive selection.