BIOCHEMICAL CYTOLOGY OF HOST-PARASITE INTERACTIONS IN PARASITIC PROTOZOA

利什曼原虫的细胞生物学研究作为一个模型， 和细胞外寄生。 重点放在表征 其表面膜（SM）的生物化学和生理功能， 分泌成分，以确定其在寄生虫生存中的作用， 发展 利什曼原虫前鞭毛体具有许多SM运输系统， 某些必需氨基酸和核苷的活跃积累。 一 其中，在L. 使用几种放射性标记的，亲和结合的，交叉的， 连接试剂。 这种外部导向的SM蛋白具有明显的 目前正在表征分子量为30 kDa。 两 分子和免疫化学方法被用来鉴定基因 编码2个利什曼原虫L-脯氨酸转运系统。 利什曼原虫和 Crithidia都显示使用S-腺苷甲硫氨酸作为蛋白质 甲基化剂 在这两种锥虫中， 是一种改变/调节某些SM活性的机制， 蛋白质在原位 L.多诺万尼前鞭毛体是 纯化至均一。 底物特异性，金属阳离子 对该38 kDa糖蛋白的需求和抑制剂进行了表征。 三个独立的糖基化事件在本研究期间被鉴定。 利什曼原虫分泌型酸性磷酸酶（SAcP）的生物合成。 的 最后一个包括[PO 4 - 6 Galbeta 1，4 Man]n的高尔基体碱基加成， SM脂磷酸聚糖（LPG）的重复组成型表位。 LPG生物合成的终末阶段也发生在高尔基体中 车厢 消减文库的遗传分析被用于 鉴定参与LPG表达的基因。 cDNA克隆正在测序 来鉴定SAcP基因的全长拷贝 体外培育 无鞭毛体被用作寄生虫基因调控的模型， 分化与发展。

The cell biology of Leishmania is investigated as a model of both intra- and extracellular parasitism. Emphasis is placed on characterizing the biochemical and physiological functions of its surface membrane (SM) and secreted components toward defining their roles in parasite survival and development. Leishmania promastigotes possess a number of SM transport systems for the active accumulation of certain essential amino acids and nucleosides. One of these, a putative SM adenosine transporter was identified in situ in L. donovani promastigotes using several radiolabeled, affinity-binding, cross- linking reagents. This externally oriented SM protein has an apparent molecular weight of 30 kDa is currently being characterized. Both molecular and immunochemical approaches are being used to identify genes coding for the 2 leishmanial L-proline transport systems. Leishmania and Crithidia were both shown to use S-adenosyl-methionine as a protein methylating agent. In both of these trypanosomatids, methylation appears to be a mechanism for modifying/regulating the activity of certain SM proteins in situ. The SM 3'-nucleotidase of L. donovani promastigotes was purified to homogeneity. The substrate specificity, metal cation requirements and inhibitors of this 38 kDa glycoprotein were characterized. Three separated glycosylation events were identified during the biosynthesis of the leishmanial secretory acid phosphatase (SAcP). The last of these includes the Golgi-bases addition of [PO4-6Galbeta1,4Man]n, the repetitive, constitutive epitope of the SM lipophosphoglycan (LPG). Terminal stages in LPG biosynthesis were also shown to occur in the Golgi compartment. Genetic analyses of subtractive libraries is being used to identify genes involved in LPG expression. cDNA clones are being sequenced to identify the full length copy of the SAcP gene. In vitro cultivated amastigotes are being used as a model of parasite gene regulated differentiation and development.