Study of glycosylation mechanism and virulence of glycoproteins produced by streptococci

人类牙齿表面的戈登链球菌与牙菌斑的形成和感染性心内膜炎有关。我们曾报道该细菌的唾液酸结合黏附素（Hsa）是一种含n -乙酰基糖胺的糖蛋白，其糖基化区是Hsa的富ser重复结构域，并以o -糖基化方式与乙二醇结合。编码hsa的基因hsa的插入突变导致该生物的感染率显著降低，并导致实验性心内膜炎大鼠主动脉瓣的炎症反应，这表明hsa有助于该生物对心脏瓣膜的感染性。估计了血小板和红细胞凝集在感染性心内膜炎中的作用。我们已经明确指出，该细菌的血小板对Hsa的受体是两种内在膜asialo-糖蛋白。结果表明，Hsa与α2-3-链唾液酸的相互作用主要由红细胞膜蛋白控制。我们还证实红细胞表面唾液糖蛋白，糖蛋白A和带3是Hsa的受体。为了寻找与Hsa糖基化相关的基因，我们筛选了S. gordonii的转座子突变文库，并在其他细菌中鉴定了编码与细胞壁合成有关的磷酸氨基葡萄糖变化酶的glmM基因。该细菌的插入型glmM突变体不产生glmM，其生长速度约为野生型的一半。形态学分析表明，glmM突变导致链球菌链延长，细菌细胞增大，细胞表面粗糙度增加。此外，与野生型相比，glmM突变减少了生物膜的形成，增加了对青霉素的敏感性。这些结果表明，glmM突变似乎影响与肽聚糖合成相关的表型。我们目前正在研究GlmM的功能与Hsa糖基化的关系。少

Streptococcus gordonii on the human tooth surface is associated with the formation of dental plaque and infectious endocarditis. We have previously reported that sialic acid-binding adhesin (Hsa) of this bacterium is a N-acetyl-glycosamine containing-glycoprotein, in which glycosylated region is Ser-rich repeat domain of Hsa, and is bound to glycol with O-glycosylation manner. An insertional mutation in hsa, the gene encoding Hsa, resulted in a significant reduction of the infection rate of the organism and an inflammatory reaction in the rat aortic valve with experimental endocarditis, suggesting that the Hsa contributes to the infectivity of the organism for heart valves. The contribution of the agglutination of platelet and erythrocyte on infectious endocarditis is estimated. We have 〓viously indicated that the receptor of platelet to Hsa of this bacterium is two kind of intrinsic membrane asialo-glycoprotein. We found that the interaction between Hsa and α2-3-linked sialic acid con … More tained by erythrocyte membrane proteins. We also confirmed that erythrocyte surface sialoglycoproteins, glycophorin A and band 3, are the receptor for Hsa. For finding the gene related to the glycosylation of Hsa, we have screened the transposon-mutation library of S. gordonii, and we identified the glmM gene encoding the phosphoglucosamine mutase which is concerned of the synthesis of cell wall in other bacteria. Insertional glmM mutant of this bacterium did not produce GlmM, and had a growth rate of about half of the wild type. Morphological analysis indicated that the glmM mutation causes elongation of the streptococcal chains, enlargement of bacterial cells, and increased roughness of the cell surface. Furthermore, glmM mutation reduces biofilm formation and increases sensitivity to penicillin relative to wild type. These results suggested that mutation in glmM appears to influence the phenotype relating to the peptidoglycan synthesis. We are now studying the relationship the function of GlmM and glycosylation of Hsa. Less