5-phosphoribose 1-diphosphate synthase involved in nucleotide, histidine, and tryptophan biosynthesis. Active in heteromultimeric complexes with other 5-phosphoribose 1-diphosphate synthases (PRS2, PRS3, PRS4 and PRS5). ATP + D-ribose 5-phosphate = 5-phospho-alpha-D-ribose 1-diphosphate + AMP + H(+) Metabolic intermediate biosynthesis; 5-phospho-alpha-D-ribose 1-diphosphate biosynthesis; 5-phospho-alpha-D-ribose 1-diphosphate from D-ribose 5-phosphate (route I): step 1/1. Cells fail to arrest in G1, cells remain budded and a significant fraction has a G2 DNA content. In such conditions, deletion mutants have a disorganized actin cytoskeleton and actin accumulates in one or two intensely staining clumps per cell. Deletion mutants also show defects in ion homeostasis and cell integrity. They fail to grow on medium containing 1.0 M NaCl, 5 mM caffeine or when incubated at 37 degrees Celsius. The caffeine and temperature sensitivity are rescued by supplementing the growth medium with 1.0 M sorbitol. Belongs to the ribose-phosphate pyrophosphokinase family.