Coupling of mitochondrial translation with the formation of respiratory complexes in yeast mitochondria

In contrast to most other eukaryotic organisms, yeast can survive without r espiration. This ability has been exploited to investigate nuclear genes re quired for expression of mitochondrial DNA. Availability of complete Saccha romyces cerevisiae genomic sequence has provided additional help in detaile d molecular analysis. Seven of the eight major products encoded by mitochon drial DNA are hydrophobic subunits of respiratory complexes in the inner me mbrane. Localization of the translation process in the same cellular compar tment ensures synthesis of mitochondrially encoded proteins near sites of t heir assembly into multimeric respiratory complexes. Association of mitocho ndrial ribosomes with the membrane is mediated by mRNA-specific translation al activators, that are involved in the recognition of initation codon. The newly synthesized mitochondrial proteins are transferred to membrane by a specific export system. This review discusses the role of membrane-localize d factors responsible for quality control and turnover of mitochondrially s ynthesized subunits as well as for assembly of respiratory complexes.