GLYCOSYL TRANSFERASE FROM STREPTOCOCCUS SANGUIS

血链球菌血小板聚集相关蛋白（PAAP） 已被分离为前体N-甲酰甲硫氨酰糖蛋白115 kDa。 虽然其他原核糖蛋白已被提出， 在文献中，这是第一个来自革兰氏阳性生物体的蛋白质， 直接实验证据表明， 糖类。 初步研究还表明， 聚合物不以PAAP的壁缔合形式存在。 因此，我们认为， 通过对PAAP生物合成和输出的研究，S. sanguis提供了一个独特的 研究原核生物新的生物合成途径的模型系统 糖蛋白 我们假设PAAP提供了一种机制， 碳水化合物聚合物附着在S. sanguis。 充当 作为协同转运蛋白，PAAP可以将碳水化合物转运通过膜 与输出的蛋白质共价结合。 一旦PAAP 在转运的过程中，碳水化合物寡糖可以从糖链中裂解出来。 蛋白质骨架并转移到其他细胞壁组分，如 脂质或肽聚糖。 因此，我们研究的长期目标是 描绘细胞壁相关的生物合成途径， 链球菌糖蛋白 本研究项目的具体目标 是分离出S血糖基转移酶及其基因。 未来 然后研究将描绘糖基化途径（包括其他糖基化途径）。 酶，糖基化的蛋白质共有序列，阳离子 要求、pH值要求等），确定糖基化是否 是共翻译和/或共转运事件，并比较这个新的 糖基化途径与已知的真核生物途径。

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.