Schneiter Roger, Carter Andrew T, Hernando Yolanda, Zellnig Günther, Schweizer Lilian M, Schweizer Michael
Institut für Biochemie und Lebensmittelchemie, Technische Universität Graz, Petersgasse 12/II, A-8010 Graz, Austria2.
Genetics and Microbiology Dept, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK3.
Microbiology (Reading). 2000 Dec;146 Pt 12:3269-3278. doi: 10.1099/00221287-146-12-3269.
Phosphoribosyl-pyrophosphate synthetase (Prs) catalyses the synthesis of phosphoribosyl pyrophosphate (PRPP), an intermediate in nucleotide metabolism and the biosynthesis of the amino acids histidine and tryptophan. The Saccharomyces cerevisiae genome contains a family of five PRS genes, PRS1-PRS5. Using anti-peptide antisera directed against two different epitopes of Prs1p it was shown that Prs1p localizes to granular cytoplasmic structures. This localization was confirmed by living cell microscopy of strains expressing a functional green fluorescent protein (GFP)-tagged Prs1p. Analysis of Prs1p distribution in conditional secretory-deficient (sec) mutants suggested that the observed distribution of Prs1p is independent of the secretory pathway. Electron microscopy revealed that plasma membrane invaginations and accumulation of cytoplasmic vesicles were more frequent in strains which lack some of the PRS genes than in the wild-type. The fact that Deltaprs1 and Deltaprs3 are hypersensitive to caffeine and unable to recover from exposure to it as judged by the release of alkaline phosphatase points to a possible link between Prs and the maintenance of cell integrity.
磷酸核糖焦磷酸合成酶（Prs）催化磷酸核糖焦磷酸（PRPP）的合成，PRPP是核苷酸代谢以及氨基酸组氨酸和色氨酸生物合成中的一种中间体。酿酒酵母基因组包含一个由五个PRS基因（PRS1 - PRS5）组成的家族。使用针对Prs1p两个不同表位的抗肽抗血清表明，Prs1p定位于颗粒状细胞质结构。通过对表达功能性绿色荧光蛋白（GFP）标记的Prs1p的菌株进行活细胞显微镜观察，证实了这种定位。对条件性分泌缺陷（sec）突变体中Prs1p分布的分析表明，观察到的Prs1p分布与分泌途径无关。电子显微镜显示，与野生型相比，缺乏某些PRS基因的菌株中质膜内陷和细胞质小泡的积累更为频繁。根据碱性磷酸酶的释放判断，Δprs1和Δprs3对咖啡因高度敏感且暴露于咖啡因后无法恢复，这一事实表明Prs与细胞完整性的维持之间可能存在联系。
