Coiled Coil Domain-containing Protein 56 (CCDC56) Is a Novel Mitochondrial Protein Essential for Cytochrome c Oxidase Function

Abstract

Background: Cytochrome c oxidase (COX), the final enzyme of the mitochondrial electron transport chain, requires several assembly factors for its proper function. Results: ccdc56 knock-out flies showed developmental delay, lethality, and a dramatic decrease in the levels/activity of COX.

hCOA3 Stabilizes Cytochrome c Oxidase 1 (COX1) and Promotes Cytochrome c Oxidase Assembly in Human Mitochondria

“…hCOA3 Is a Transmembrane Protein of the Inner Mitochondrial Membrane-We have recently shown CCDC56 to be a mitochondrial protein essential for COX activity in D. melanogaster (20), although its precise function remained to be elucidated. BLAST alignments showed this protein is well conserved from Drosophila to humans, and more recent studies have suggested CCDC56 is the homologue of yeast Coa3 (18).…”

“…Mitochondrial Subfractionation and Proteinase K Protection Assays-Mitochondria were purified from HeLa cells expressing hCOA3-FLAG as described previously (20). Mitochondria were ruptured by sonication.…”

“…Activity of the OXPHOS Complexes-The activity of the OXPHOS complexes and the enzyme citrate synthase were determined as described previously (20).…”

“…Immunoprecipitation and Proteomic Analysis-Mitochondria were purified from HeLa cells expressing hCOA3-FLAG or containing empty pIRESpuro2 vector as described previously (20). Equal amounts of mitochondrial protein of each cell line were lysed using 1% DDM in 50 mM Tris HCl pH 7.4, 150 mM NaCl and 1 mM EDTA.…”

“…We have recently identified a mitochondrial protein in Drosophila melanogaster, CCDC56, encoded on a bicistronic mRNA with mitochondrial translation factor B1 (20). This protein is essential for COX activity in Drosophila and is highly conserved throughout evolution.…”