MOLECULAR BIOLOGY, PLATELET AGGREGATION, S. SANGUIS

某些草绿色链球菌菌株（Agg+）， 包括口腔粘膜植物群的主要成员， 血链球菌在体外诱导人血小板聚集。 当 草绿色链球菌进入体内，它们可能会变得显著 病原体或甚至某些严重人类疾病的病原体， 与血小板相互作用，如细菌性心内膜炎、白塞病 综合征等 S.血吸虫（Adh+，Agg+） 建议参与与血小板的相互作用，这是类 I类抗原（粘附素），II类抗原，也称为 血小板聚集相关蛋白（PAAP），和III类抗原， 其具有胞外ATP酶活性。 S.血细胞与血小板结合， I类抗原，然后II类抗原触发并激活 致密颗粒的释放和血小板的聚集， III抗原通过水解从致密的胶原蛋白中释放的ATP来放大反应。 颗粒转化为ADP。 虽然已经鉴定了PAAP的各种无细胞形式，但是这些无细胞形式的PAAP是不稳定的。 分子不直接诱导血小板聚集。 直接证据 需要提供证明细胞表面的PAAP作为 一种激活和聚集血小板的独特因子。 具体目标 该项目迄今已完成的包括（1）开发 分离S.血液使用 转座子Tn 916和等基因回复突变体;（2）克隆PAAP基因（paap） 来自酿脓链球菌（3）分离和纯化重组体的部分， PAAP（rPAAP）基因在大肠杆菌中表达。coli中进行比较， 功能上与分离自S. sanguis， (4)对该基因进行部分测序，以及（5）通过以下方式表征该基因： 使用特定测序软件分析测序数据， 与基因库比对。 需要进一步研究 测序并制备S. sanguis。

Certain strains of viridans streptococci (Agg+), including the predominant member of the oral commensal flora, Streptococcus sanguis, induce human platelets to aggregate in vitro. When viridans streptococci entered the body, they may become significant pathogens or even etiological agents of certain severe human diseases by interacting with platelets, such as bacterial endocarditis, Behcet's syndrome, etc Three different surface antigens of S. sanguis (Adh+, Agg+) have been proposed to be involved in the interaction with platelets, which are class I antigen (adhesin), class II antigen, which is also called platelet-aggregation associated protein (PAAP), and class III antigen, which has ecto-ATPase activity. S. sanguis cells bind to platelets by class I antigen, and then class II antigen triggers and activates the release of the dense granules and the aggregation of platelets, the class III antigen amplifies the reaction by hydrolyzing ATP released from dense granules into ADP. Although various cell-free forms of PAAP have been identified, these molecules do not directly induce platelet aggregation. Direct evidence needs to be provided to prove that PAAP on the cell surface functions as an unique factor to activate and aggregate platelets. The specific aims of this project which so far have been accomplished includes (1) developed procedures for isolating an isogenic PAAP mutant of S. sanguis using transposon Tn916 and isogenic revertants, (2) cloned the PAAP gene (paap) from S. sanguis, (3) isolated and purified the portion of the recombinant PAAP (rPAAP) expressed by the cloned gene in E. coli and compared it functionally with the cell-free forms of PAAP isolated from S. sanguis, (4) partially sequenced the gene, and (5) characterized the gene by analyzing the sequencing data using specific sequencing software and comparing the sequence with genebanks. Further studies need to be done on sequencing and making a gene specific insertional mutant of S. sanguis.