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The importance of the five phosphoribosyl-pyrophosphate synthetase (Prs) gene products of Saccharomyces cerevisiae in the maintenance of cell integrity and the subcellular localization of Prs1p

Department of Biological Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK¹
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
Institut für Pflanzenphysiologie, Karl-Franzens Universität, Schubertstrasse 51, A-8010 Graz, Austria⁴

Author for correspondence: Michael Schweizer. Tel: +44 131 451 3186. Fax: +44 131 451 3009. e-mail: M.Schweizer{at}hw.ac.uk

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 prs1 and prs3 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.

Keywords: phosphoribosyl-pyrophosphate synthetase (Prs), subcellular localization of Prs1p, cell integrity, Saccharomyces cerevisiae

Abbreviations: DIC, differential interference contrast; 5-FOA, 5-fluoroorotic acid; GFP, green fluorescent protein; NHR, non-homologous region; PRPP, 5-phosphoribosyl 1()-pyrophosphate; Prs, 5-phosphoribosyl-1()-pyrophosphate synthetase; RLU, relative light units

This article has been cited by other articles:

				K. Wang, S. Vavassori, L. M. Schweizer, and M. Schweizer Impaired PRPP-synthesizing capacity compromises cell integrity signalling in Saccharomyces cerevisiae Microbiology, October 1, 2004; 150(10): 3327 - 3339. [Abstract] [Full Text] [PDF]