title: The conserved mitochondrial twin Cx9C protein Cmc2 Is a Cmc1 homologue essential for cytochrome c oxidase biogenesis.
abstract: Mitochondrial copper metabolism and delivery to cytochrome c oxidase and mitochondrially localized CuZn-superoxide dismutase (Sod1) requires a growing number of intermembrane space proteins containing a twin Cx(9)C motif. Among them, Cmc1 was recently identified by our group. Here we describe another conserved mitochondrial metallochaperone-like protein, Cmc2, a close homologue of Cmc1, whose function affects both cytochrome c oxidase and Sod1. In the yeast Saccharomyces cerevisiae, Cmc2 localizes to the mitochondrial inner membrane facing the intermembrane space. In the absence of Cmc2, cytochrome c oxidase activity measured spectrophotometrically and cellular respiration measured polarographically are undetectable. Additionally, mutant cmc2 cells display 2-fold increased mitochondrial Sod1 activity, whereas CMC2 overexpression results in Sod1 activity decreased to 60% of wild-type levels. CMC1 overexpression does not rescue the respiratory defect of cmc2 mutants or vice versa. However, Cmc2 physically interacts with Cmc1 and the absence of Cmc2 induces a 5-fold increase in Cmc1 accumulation in the mitochondrial membranes. Cmc2 function is conserved from yeast to humans. Human CMC2 localizes to the mitochondria and CMC2 expression knockdown produces cytochrome c oxidase deficiency in Caenorhabditis elegans. We conclude that Cmc1 and Cmc2 have cooperative but nonoverlapping functions in cytochrome c oxidase biogenesis.
authors.affiliation: Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
authors.forename: Darryl
authors.initials: D
authors.lastname: Horn
authors.affiliation: Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Laboratorio di Oncoematologia Pediatrica, Dipartimento di Pediatria, University of Padova, 35128 Padova, Italy.
authors.forename: Eva
authors.initials: E
authors.lastname: Trevisson
authors.affiliation: Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
authors.forename: Hassan
authors.initials: H
authors.lastname: Al-Ali
authors.affiliation: Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Harris
authors.affiliation: Laboratorio di Oncoematologia Pediatrica, Dipartimento di Pediatria, University of Padova, 35128 Padova, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Salviati
authors.affiliation: Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy; Departments of Neurology, University of Miami Miller School of Medicine, Miami, Florida 33136. Electronic address: abarrientos@med.miami.edu.
authors.forename: Antoni
authors.initials: A
authors.lastname: Barrientos
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence; D017931:DNA Primers; D003576:Electron Transport Complex IV / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV