Figure 1.

Growth phenotypes of the eight spontaneous cox18 alleles obtained by selection for Arg⁺Pet⁻ (retention of the Arg8p moiety of a Cox2p-Arg8p fusion protein within the matrix). Cells with the indicated relevant mitochondrial genotypes were grown on solid complete glucose medium (YPD) then replica plated twice to glucose medium lacking arginine (−ARG) and complete medium containing ethanol and glycerol (YPEG), as indicated. Incubation temperature was 30^o. The mtDNA of these strains encoded either the Cox2p-Arg8p fusion protein or wild-type Cox2p, as indicated. All Cox2p-Arg8p–expressing strains are isogenic to strain SCS15a and all Cox2p-expressing strains are isogenic to TMD28 (Table 1). cox18Δ strains are SCS32 and RCB1. f.s. indicates a frame-shift affecting the indicated codon.