Phenotypes of yeast mutants lacking the mitochondrial protein Pet20p

The pet20 ‐Δ deletion in Saccharomyces cerevisiae causes diminished growth on media containing non‐fermentable carbon sources when incubated at both above and below the 30 °C optimal growth temperature. Furthermore, the pet20 ‐Δ strain has a greatly reduced level of cytochrome c , especially at 37 °C. The pet20 ‐Δ strain was sensitive to high NaCl and CaCl 2 concentrations, hydrogen peroxide, oligomycin, polymixin B, amphotericin B and fluconazole. Biochemical fractionation and immunofluorescence staining demonstrated that Pet20p is located primarily in the mitochondria. Rhodamine B staining of pet20 ‐Δ cells showed an altered mitochondrial staining, indicating the possible lack of the mitochondrial membrane potential. We suggest that PET20 encodes a protein required for proper assembly or maintenance of mitochondrial components, but does not serve an enzymatic role. It is also possible that Pet20p may constitute a non‐catalytic subunit of an uncharacterized mitochondrial complex or serve as a transporter or a coupling factor. Copyright © 2006 John Wiley & Sons, Ltd.