Figure 1.

mS38 is specifically required for the efficient translation of COX1, COX2, and COX3 mRNAs. See also Supplementary Figure S1. The intronless WT (W303 I⁰) and ΔmS38 mutant strains were characterized by: (A) Serial dilutions growth test in fermentable complete solid media containing glucose (YPD) and respiratory media containing ethanol and glycerol (YPEG). Pictures were taken after two days of growth at 30°C. (B) Measurement of OXPHOS parameters in the indicated cell strains. The graph shows the endogenous cell respiration rate (CR), and the enzymatic activities of CIV or cytochrome c oxidase (COX) and of NADH-cytochrome c reductase (NCCR), expressed as the percentage of WT. Bars represent the mean ± SD of three independent repetitions. (C) Steady‐state levels of OXPHOS complexes extracted from isolated mitochondria with lauryl maltoside, analyzed by BN–PAGE and detected by immunoblotting with the indicated antibodies. (D) Immunoblot analyses of the steady-state levels of the indicated complex III (CIII) and complex IV (CIV) subunits and assembly factors. Porin was used as loading control. (E) Metabolic labeling with ³⁵S-methionine (2.5 μCi; 4.30 nM) + cold methionine (12.90 nM) of newly synthesized mitochondrial products in whole cells during increasing pulse times in the presence of cycloheximide to inhibit cytoplasmic protein synthesis. Immunoblotting for Porin was used as a loading control. Newly-synthesized polypeptides are identified on the right. In the lower panel, raw densitometry values for the indicated individual proteins were plotted to visualize their synthesis kinetics. (F) RT-qPCR analysis of mitochondrial RNA steady-state levels in WT (W303 I⁰) and ΔmS38 cells, expressed as fold change versus WT values. The bars represent the average ± SD of three independent repetitions. Student's t-test: *P < 0.01.