A Missense Mutation of Cytochrome Oxidase Subunit II Causes Defective Assembly and Myopathy

• Published in: American journal of human genetics 1999-10, Vol.65 (4), p.1030-1039
• Main Authors: Rahman, Shamima, Taanman, Jan-Willem, Cooper, J. Mark, Nelson, Isabelle, Hargreaves, Ian, Meunier, Brigitte, Hanna, Michael G, García, José J., Capaldi, Roderick A., Lake, Brian D., Leonard, James V., Schapira, Anthony H.V.
• Format: Article
• Language: English
• Subjects: Acidosis, Lactic - enzymology; Acidosis, Lactic - genetics; Acidosis, Lactic - metabolism; Acidosis, Lactic - pathology; Adolescent; Amino Acid Sequence; Amino Acid Substitution - genetics; Base Sequence; Biological and medical sciences; Blotting, Western; Cell Nucleus - enzymology; Cell Respiration; Cells, Cultured; Cytochrome oxidase; Cytochrome-c Oxidase Deficiency; DNA, Mitochondrial - genetics; Electron Transport Complex IV - chemistry; Electron Transport Complex IV - genetics; Electron Transport Complex IV - metabolism; Enzyme Stability; Errors of metabolism; Heme - analogs & derivatives; Heme - metabolism; Holoenzymes - chemistry; Holoenzymes - deficiency; Holoenzymes - genetics; Holoenzymes - metabolism; Humans; Immunohistochemistry; Male; Medical sciences; Metabolic diseases; Miscellaneous hereditary metabolic disorders; Mitochondria; Mitochondria - enzymology; Mitochondria - genetics; Mitochondria - metabolism; Mitochondria - pathology; Models, Molecular; Molecular Sequence Data; mtDNA; Muscles - enzymology; Muscles - metabolism; Muscles - pathology; Muscular Diseases - enzymology; Muscular Diseases - genetics; Muscular Diseases - metabolism; Muscular Diseases - pathology; Mutation, Missense - genetics; Myopathy; Photolysis; Polarography; Protein Structure, Quaternary; Sequence Alignment
• ISSN: 0002-9297; 1537-6605
• DOI: 10.1086/302590

We report the first missense mutation in the mtDNA gene for subunit II of cytochrome c oxidase (COX). The mutation was identified in a 14-year-old boy with a proximal myopathy and lactic acidosis. Muscle histochemistry and mitochondrial respiratory-chain enzymology demonstrated a marked reduction in COX activity. Immunohistochemistry and immunoblot analyses with COX subunit–specific monoclonal antibodies showed a pattern suggestive of a primary mtDNA defect, most likely involving CO II, for COX subunit II (COX II). mtDNA-sequence analysis demonstrated a novel heteroplasmic T→A transversion at nucleotide position 7,671 in CO II. This mutation changes a methionine to a lysine residue in the middle of the first N-terminal membrane-spanning region of COX II. The immunoblot studies demonstrated a severe reduction in cross-reactivity, not only for COX II but also for the mtDNA-encoded subunit COX III and for nuclear-encoded subunits Vb, VIa, VIb, and VIc. Steady-state levels of the mtDNA-encoded subunit COX I showed a mild reduction, but spectrophotometric analysis revealed a dramatic decrease in COX I–associated heme a 3 levels. These observations suggest that, in the COX protein, a structural association of COX II with COX I is necessary to stabilize the binding of heme a 3 to COX I.