title: Identification of Cox20p, a novel protein involved in the maturation and assembly of cytochrome oxidase subunit 2.
abstract: We have identified Cox20p, a 23.8-kDa protein of the mitochondrial inner membrane that is involved in the biogenesis of the yeast cytochrome oxidase complex. Cytochrome oxidase subunit 2 (Cox2p) accumulates as a precursor in cox20 mutants, suggesting a defect in biogenesis of this mitochondrially encoded protein. The inability of cox20 mutants to process the subunit 2 precursor (pCox2p) is not due to impaired export of the protein across the inner membrane or to an inactive Imp1p/Imp2p peptidase. Rather, Cox20p specifically binds the newly synthesized pCox2p, a step required to present the exported pCox2p as a substrate to the Imp1p peptidase. All of the endogenous pCox2p accumulated in an Deltaimp1 mutant, and a small fraction of Cox2p in wild type yeast, is detected in a complex with Cox20p. Following maturation Cox2p remained associated with Cox20p, prior to assembling into the cytochrome oxidase complex. We propose that Cox20p acts as a membrane-bound chaperone necessary for cleavage of pCox2p and for interaction of the mature protein with other subunits of cytochrome oxidase in a later step of the assembly process.
authors.affiliation: Institut für Physiologische Chemie der Universität München, Goethestrasse 33, 80336 München, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Hell
authors.forename: A
authors.initials: A
authors.lastname: Tzagoloff
authors.forename: W
authors.initials: W
authors.lastname: Neupert
authors.forename: R A
authors.initials: RA
authors.lastname: Stuart
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
chemical_list: C405324:Cox20 protein, S cerevisiae; D017931:DNA Primers; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV