Figure 5.

Deletion of ₂₈₄KKCPK₂₈₈ from Prs3 reduces PRPP synthetase activity. YN94–1 (WT) and YN96–77 (prs3Δ) transformed with pGAD, pGAD-Prs3, Tc4(pGAD-prs3-ΔKKCPK) or Tc10(pGAD-prs3-ΔKKCPK) were grown o/n from a single colony at 30°C in 10 ml SC-leu or YEPD for WT. Cell extracts were prepared as described in the Materials and Methods section. Following protein determination and pre-incubation of the reaction buffer at 37°C for 30 min, the reaction was started by the addition of ribose-5-phosphate and appropriate amounts of extracts dispensed into a 96-well plate. The results are expressed as μmol min⁻¹ mg⁻¹. The significance levels of YN96–77 [pGAD-Prs3] and YN96–77 [Tc4/10(pGAD-prs3-ΔKKCPK)] are calculated with respect to the specific activity of YN96–77 [pGAD]. Data are shown as mean ± SD. Number of measurements for each transformant: WT, pGAD-Prs3, Tc4(pGAD-prs3-ΔKKCPK) (n = 3) and for pGAD, Tc10(pGAD-prs3-ΔKKCPK) (n = 5). For illustration purposes, the data for Tc4(pGAD-prs3-ΔKKCPK) and Tc10(pGAD-prs3-ΔKKCPK) have been combined (Tc4/Tc10(pGAD-prs3-ΔKKCPK). P-values: * = P ≤ 0.05, ** = P ≤ 0.01, ns = not significant.