Overexpression of USB1 compensates for a respiratory deficiency. Panel A: The thermosensitive mutant oxa1-E65GF229S  was transformed with high-copy plasmids carrying the wild type OXA1 gene or the USB1 gene, or the empty control vector (vector). The transformants were spotted onto fermentable (glucose) and respiratory (glycerol/ethanol) medium. The plates were incubated for five days at 36°C. Panel B: Cytochrome absorption spectra of the oxa1 cells transformed with the high copy plasmids carrying OXA1 or YLR132, grown on respiratory medium for 2 or 5 days at 36°C. Cytochrome c1 and b are part of respiratory complex III while cytochromes a+aa3 are part of complex IV.