MOLECULAR GENETICS OF YEAST SEXUAL AGGLUTININS

酿酒酵母交配过程中的细胞-细胞接触 由细胞表面黏附糖蛋白介导，称为α-和α- 凝集素，由a和α交配型细胞表达， 分别进行了分析。据预测，α-凝集素的结构类似于 哺乳动物细胞黏附蛋白的免疫球蛋白超家族， 这表明阐明酵母中黏附蛋白的相互作用将 对高等真核生物有影响。提议的一个重要目标 研究的目的是描述黏附蛋白之间的相互作用。诱变 α-凝集素粘附域的信息，基于 一种结构模型，正在被用来确定涉及到的残基 粘附性和蛋白质的结构。这种方法将是 延伸到α-凝集素粘附亚单位。它的特殊性 高等真核生物中黏附蛋白的相互作用对 特异性病毒-细胞、细胞-细胞和细胞-细胞外基质 互动。其他种类的萌芽酵母表达凝集素， 与酿酒酵母凝集素具有相同的生化特征；然而 凝集素的相互作用显示出物种特异性。基因的克隆 克鲁维氏酵母凝集素结构基因将促进 黏附蛋白的结构模拟和物种研究 专一性。将构建酿酒酵母/克鲁维里葡萄球菌的杂交基因 并对功能和特异性进行测试，这些基因将被诱变 并筛选特异性改变突变体以识别残留物 涉及到专一性的。拟议研究的最终目标包括 凝集素的细胞壁定位机制分析。 α-凝集素通过连接到细胞膜被运输到质膜 一种糖基磷脂酰肌醇锚定，之后有一种新的作用机制 把它转移到细胞壁上。α-凝集素细胞的性质 壁链将被表征，并且α-凝集素序列 将确定参与这一目标机制的人员。此外, 将进行突变筛选以确定与此相关的酶 新的机制。这种α-细胞壁附着的机制 凝集素与细胞壁甘露糖蛋白的一般定位有关。 因为其他真菌的细胞壁结构与酵母相似， 酿酒酵母细胞壁生物发生机制的研究 可能导致治疗药物的发展，以对抗医学上的 重要的真菌。

Cell-cell contact during mating in the yeast Saccharomyces cerevisiae is mediated by cell surface adhesion glycoproteins, called a- and alpha- agglutinin, which are expressed by cells of a and alpha mating type, respectively. Alpha-agglutinin is predicted to have a structure similar to the immunoglobulin superfamily of mammalian cell adhesion proteins, suggesting that elucidation of adhesion protein interactions in yeast will have implications for higher eukaryotes. An important goal of the proposed research is to characterize the adhesion protein interactions. Mutagenesis of the alpha-agglutinin adhesion domain, based on information provided by a structural model, is being used to identify residues involved in adhesion and in the structure of the protein. This approach will be extended to the alpha-agglutinin adhesion subunit. The specificity of adhesion protein interactions in higher eukaryotes is critical for specific viral-cell, cell-cell, and cell-extracellular matrix interactions. Other species of budding yeast express agglutinins that share biochemical features with the S. cerevisiae agglutinins; however agglutinin interactions show species specificity. The cloning of agglutinin structural genes from the yeast S. kluyveri will facilitate structural modeling of the adhesion proteins and studies of species specificity. Hybrid S. cerevisiae/S. kluyveri genes will be constructed and tested for function and specificity, and the genes will be mutagenized and screened for change-of-specificity mutants to identify residues involved in specificity. The final goal of the proposed research involves an analysis of the mechanism of cell wall localization of the agglutinins. Alpha-agglutinin is transported to the plasma membrane through linkage to a glycosyl phosphatidylinositol anchor, after which a novel mechanism acts to transfer it to the cell wall. The nature of the alpha-agglutinin-cell wall linkage will be characterized, and the alpha-agglutinin sequences involved in this targeting mechanism will be identified. In addition, mutant screens will be undertaken to identify enzymes involved in this novel mechanism. This mechanism of cell wall attachment of alpha- agglutinin is implicated in general cell wall mannoprotein localization. Because cell wall structure in other fungi is similar to yeast, investigation of the mechanism of cell wall biogenesis in S. cerevisiae may lead to the development of therapeutic agents against medically important fungi.