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Reference: Torello AT, et al. (1997) Deletion of the leader peptide of the mitochondrially encoded precursor of Saccharomyces cerevisiae cytochrome c oxidase subunit II. Genetics 145(4):903-10

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Abstract

Cytochrome c oxidase subunit II (Cox2p) of Saccharomyces cerevisiae is synthesized within mitochondria as a precursor, pre-Cox2p. The 15-amino acid leader peptide is processed after export to the intermembrane space. Leader peptides are relatively unusual in mitochondrially coded proteins: indeed mammalian Cox2p lacks a leader peptide. We generated two deletions in the S. cerevisiae COX2 gene, removing either the leader peptide (cox2-20) or the leader peptide and processing site (cox2-21) without altering either the promoter or the mRNA-specific translational activation site. When inserted into mtDNA, both deletions substantially reduced the steady-state levels of Cox2p and caused a tight nonrespiratory phenotype. A respiring pseudorevertant of the cox2-20 mutant was heteroplasmic for the original mutant mtDNA and a p- mtDNA whose deletion fused the first 251 codons of the mitochondrial gene encoding cytochrome b to the cox2-20 sequence. The resulting fusion protein was processed to yield functional Cox2p. Thus, the presence of amino-terminal cytochrome b sequence bypassed the need for the pre-Cox2p leader peptide. We propose that the pre-Cox2p leader peptide contains a targeting signal necessary for membrane insertion, without which it remains in the matrix and is rapidly degraded.

Reference Type
Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, Non-P.H.S. | Research Support, U.S. Gov't, P.H.S. | Comparative Study
Authors
Torello AT, Overholtzer MH, Cameron VL, Bonnefoy N, Fox TD
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