Bielefeld M, Hollenberg C P
Institut für Mikrobiologie, Universität Düsseldorf, Federal Republic of Germany.
Mol Gen Genet. 1989 Feb;215(3):401-6. doi: 10.1007/BF00427036.
Intercompartmental transport of secreted proteins in yeast was analysed using invertase mutants. Deletions and insertions at the BamHI (position + 787) or the Asp718 (position + 1159) sites of the SUC2 gene led to mutant proteins with different behaviour regarding secretion, localization and enzyme activity. The deletion mutants showed accumulation of core glycosylated material in the endoplasmic reticulum (ER) a decrease of secreted protein by 5%-30% and loss of enzyme activity. The secreted material was localized in the culture medium and not - as is normal for invertase - in the cell wall. No delay in transport from the Golgi to the cell surface was observed, indicating that the rate-limiting step for secretion is at the ER-Golgi stage. Two insertion mutants, pIPA and pIPB, retained enzyme activity. Mutant pIPB showed 10% secretion, while 60%-70% secretion was observed for pIPA. While the non-secreted material accumulated in the ER, the secreted material was present in the cell wall. The results suggest that the presence of structures incompatible with secretion leads to ER accumulation of mutated invertase.
利用转化酶突变体分析了酵母中分泌蛋白的细胞间运输。SUC2基因的BamHI（位置+787）或Asp718（位置+1159）位点的缺失和插入导致突变蛋白在分泌、定位和酶活性方面表现出不同行为。缺失突变体在内质网（ER）中显示出核心糖基化物质的积累，分泌蛋白减少5%-30%，酶活性丧失。分泌物质定位于培养基中，而不像转化酶正常情况下定位于细胞壁中。未观察到从高尔基体到细胞表面的运输延迟，表明分泌的限速步骤处于内质网-高尔基体阶段。两个插入突变体pIPA和pIPB保留了酶活性。突变体pIPB显示10%的分泌率，而pIPA的分泌率为60%-70%。当未分泌的物质在内质网中积累时，分泌的物质存在于细胞壁中。结果表明，与分泌不相容的结构的存在导致突变转化酶在内质网中积累。
