GLYCOSYL TRANSFERASE FROM STREPTOCOCCUS SANGUIS

血链球菌血小板聚集相关蛋白(PAAP) 已被分离为115的前体N-甲酰甲硫基糖蛋白 KDA。而其他原核糖蛋白已经被建议在 文献，这是第一个来自革兰氏阳性生物体的蛋白质， 直接的实验证据表明，共价关联 碳水化合物。初步研究还表明，碳水化合物 聚合物不以PAAP的壁联形式存在。因此， 通过研究PAAP的生物合成和输出，血链霉菌提供了一种独特的 研究原核生物生物合成新途径的模型系统 糖蛋白。 我们假设PAAP提供了一种合并机制 碳水化合物聚合物附着在血链霉菌细胞壁上。作为一个 共转运体，PAAP可能通过膜转运碳水化合物 与出口蛋白质共价结合。一旦PAAP 在运输过程中，碳水化合物低聚糖可以从 蛋白质骨架，并转移到其他细胞壁成分，如 脂类或肽聚糖。因此，我们研究的长期目标是 细胞壁相关蛋白生物合成途径的研究 链球菌糖蛋白。这项研究项目的具体目的 目的是分离血链球菌糖基转移酶及其基因。未来 然后，研究将描绘糖基化途径(包括其他 酶，糖基化的蛋白质共同序列，阳离子 要求、pH要求等)，决定是否糖基化 是共翻译和/或共传输事件，并将这一新的 糖基化途径与已知的真核途径。

The Streptococcus sanguis Platelet Aggregation-associated Protein (PAAP) has been isolated as a precursor N-formylmethionyl glycoprotein of 115 kDa. While other prokaryotic glycoproteins have been suggested in the literature, this is the first protein from a gram positive organism, shown by direct experimental evidence to have covalently associated carbohydrate. Preliminary studies also suggest that the carbohydrate polymers are not present in the wall-associated form of PAAP. Therefore, by studying PAAP biosynthesis and export, S. sanguis provides a unique model system to study the novel biosynthetic pathway of prokaryotic glycoproteins. We hypothesize that PAAP provides a mechanism for incorporation of carbohydrate polymers onto the cell wall of S. sanguis. Acting as a cotransporter, PAAP may translocate the carbohydrate through the membrane in covalent association with the exported protein. Once PAAP is transported, the carbohydrate oligosaccharides may be cleaved from the protein backbone and transferred to other cell wall components, such as lipid or peptidoglycan. Therefore the long-term goal of our research is to delineate the biosynthetic pathway of cell wall-associated streptococcal glycoproteins. The specific aims of this research project are to isolate the S. sanguis glycosyltransferase and its gene. Future research would then delineate the glycosylation pathway (including other enzymes, protein consensus sequence for glycosylation, cation requirements, pH requirements, etc.), determine of whether glycosylation is cotranslational and/or a cotransport event, and compare this new glycosylation pathway with known eukaryotic pathways.