STRUCTURE AND PROCESSING OF TRYPANOSOME VARIANT ANTIGENS

感染人类和动物的锥虫具有主要的医学 以及对赤道非洲的兽医影响。 失败 免疫系统消除锥虫感染， 由于唾液锥虫的独特机制， 抗原变异 每一个锥虫都被一个表面所覆盖 由大约一千万个紧密堆积的单层组成的被毛 变体表面大家族的单个成员的分子 糖蛋白（VSG）。 这项建议的目的是研究 VSG的羧基末端翻译后修饰 布氏锥虫，其中存在疏水肽尾， 在初级VSG mRNA翻译产物上，被切割， 被一种复合的聚糖肌醇磷脂所取代， VSG到表面膜。 变量的问题 VSG连接的糖脂的半乳糖基化将通过 在糖脂处延伸结构， 预期VSG的直接前体的特征- 连接糖脂将被确定，使用以前的 其特征在于VSG连接作为实验设计的模型， 方法论 有迹象表明，肽作为模型， 实验设计和方法。 有迹象表明 肽裂解和糖脂附着发生在共- 在内质网的协调反应，但进一步 聚糖侧链的加工可能发生在高尔基体中， 设备. 将开发无细胞系统， 锥虫微粒体组分，其中的细节 可以研究改性反应。 其进一步的目的是 一个建议是研究糖脂部分在VSG中的作用 分泌、功能、周转和释放。 概念和 这些方面的实验贡献，可以预期从 类似的翻译后意识的不断扩大 几种哺乳动物蛋白质的修饰。 自从锥虫 将糖脂附着在10%的蛋白质（VSG）上， 代表了一个理想的模型，在这个模型中， 修饰途径，可能是重要的所有真核生物 细胞 VSG释放酶，一种聚糖磷脂酰肌醇， 特异性磷脂酶C（GPI-PLC）将进一步表征。 将进行进一步的特异性研究，其亚细胞 将确定其位置，并通过以下方式对其活动进行监管： 将确定效应物和抑制物。 GPI-PLC基因 将被克隆和测序，用于其生物合成的研究， 监管，并促进表征相应的 哺乳动物酶

Human and animal-infective trypanosomes have major medical and veterinary consequences for equatorial Africa. Failure of the immune system to eliminate trypanosome infections is largely attributable to the Salivarian trypanosomes' unique mechanism for antigenic variations. Each trypanosome is covered by a surface coat consisting of a closely packed monolayer of about ten million molecules of a single member of a large family of variant surface glycoproteins (VSGs). The aim of this proposal is to study the carboxy-terminal post-translational modification of the VSGs of Trypanosoma brucei, whereby a hydrophobic peptide tail, present on the primary VSG mRNA translation product, is cleaved and replaced by a complex glycan inositol phospholipid, which anchors VSG to the surface membrane. The question of variable galactosylation of the VSG-linked glycolipid will be resolved by extending structural at a glycolipid having several of teh characteristic expected of an immediate precursor of the VSG- linked glycolipid will be determined, suing the previously characterized VSG-linked as a model for experimental design and methodology. There are indications that peptide as a model for experimental design and methodology. There are indications that peptide cleavage and glycolipid attachment occur in a co- ordinated reaction at the endoplasmic reticulum, but that further processing of the glycan side-chain may occur in the Golgi apparatus. Cell-free systems will be developed, using trypanosome microsomal fractions, in which details of the modification reaction can be investigated. A further aim of this proposal is to investigate the role of the glycolipid moiety in VSG secretion, function, turnover and release. Conceptual and experimental contributions to these aspects can be expected from the expanding awareness of similar post-translational modification of several mammalian proteins. Since trypanosomes attach glycolipid to 10% of their protein (the VSG), they may represent the ideal model in which to explore some aspects of a modification pathway that may be important to all eukaryotic cells. The VSG-releasing enzyme, a glycan-phosphatidylinositol- specific phospholipase C (GPI-PLC), will be further characterized. Further specificity studies will be performed, its subcellular location will be determined, and the regulation of its activity by effectors and inhibitors will be determined. The GPI-PLC gene will be cloned and sequenced, for studies of its biosynthesis, regulation, and to facilitate characterization of the corresponding mammalian enzyme.