The conserved mitochondrial twin Cx9C protein Cmc2 Is a Cmc1 homologue essential for cytochrome c oxidase biogenesis.
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.
Horn
Darryl
D
Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
Zhou
Wen
W
Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
Trevisson
Eva
E
Laboratorio di Oncoematologia Pediatrica, Dipartimento di Pediatria, University of Padova, 35128 Padova, Italy.
Al-Ali
Hassan
H
Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
Harris
Thomas K
TK
Departments of Biochemistry and Molecular Biology, University of Padova, 35128 Padova, Italy.
Salviati
Leonardo
L
Laboratorio di Oncoematologia Pediatrica, Dipartimento di Pediatria, University of Padova, 35128 Padova, Italy.
Barrientos
Antoni
A
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.
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
D017931:DNA Primers; D029701:Saccharomyces cerevisiae Proteins; D003576:Electron Transport Complex IV