A nuclear mutation prevents processing of a mitochondrially encoded membrane protein in Saccharomyces cerevisiae.

Abstract

Subunit II of cytochrome oxidase is encoded by the mitochondrial OXI1 gene in Saccharomyces cerevisiae. The temperature‐sensitive nuclear pet mutant ts2858 has an apparent higher mol. wt. subunit II when analyzed on lithium dodecylsulfate (LiDS) polyacrylamide gels. However, on LiDS‐6M urea gels the apparent mol. wt. of the wild‐type protein exceeds that of the mutant. Partial revertants of mutant ts2858 that produce both the wild‐type and mutant form of subunit II were isolated. The two forms of subunit II differ at the N‐terminal part of the molecule as shown by constructing and analyzing nuclear ts2858 and mitochondrial chain termination double mutants. The presence of the primary translation product in the mutant and of the processed form in the wild‐type lacking 15 amino‐terminal residues was demonstrated by radiolabel protein sequencing. Comparison of the known DNA sequence with the partial protein sequence obtained reveals that six of the 15 residues are hydrophilic and, unlike most signal sequences, this transient sequence does not contain extended hydrophobic parts. The nuclear mutation ts2858 preventing post‐translational processing of cytochrome oxidase subunit II lies either in the gene for a protease or an enzyme regulating a protease.

Peripheral Mitochondrial Inner Membrane Protein, Mss2p, Required for Export of the Mitochondrially Coded Cox2p C Tail in Saccharomyces cerevisiae

“…Cox2p is synthesized as a precursor protein whose N-terminal 15-amino-acid leader peptide is cleaved by the Imp peptidase complex in the IMS after translocation through the membrane (36,43,47,50).…”

Biogenesis of Mitochondrial Energy Transducing Complexes

“…Pratje et al, (1983) described a nuclear temperature-sensitive pet mutant of yeast in which the precursor accümulates. By comparing the amino-terminal protein sequences of subunit II in wild type and the mutant, an amino-terminal extension of 15 amino acid residues was found for 202 NIKOLAUS PFANNER AND WALTER NEUPERT the precursor in the mutant strain.…”

“…A considerable number of nuclear and extranuclear mutants deficient in cytochrome oxidase activity are known in N. crassa and yeast (Werner et al, 1974;Ono et al, 1975;Werner, 1977, 1979;Nargang et al, 1978;SaltzgaberMüller and Schatz, 1978;Werner and Bertrand, 1979;Pratje et al, 1983;Dowhan et al, 1985). Most of them are deficient in synthesis of one or more subunits; others contain precursor proteins with a higher apparent molecular weight (see Section III).…”

Antagonistic signals within the COX2 mRNA coding sequence control its translation in Saccharomyces cerevisiae mitochondria

“…Translation of COX2 yields pre-Cox2p, a precursor protein with a 15-residue leader peptide (Sevarino and Poyton 1980) that is cleaved during or following Cox2p assembly in the inner membrane (Pratje et al 1983). Although the leader peptide does not function strictly as a signal sequence directing translocation of a reporter protein fused downstream, it is sufficient to cause association of the fusion protein with the inner membrane (He and Fox 1997).…”