A missense mutation of cytochrome oxidase subunit II causes defective assembly and myopathy.
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 a3 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 a3 to COX I.
Rahman
S
S
University Department of Clinical Neurosciences, Royal Free and University College Medical School, Rowland Hill Street, London, United Kingdom.
Taanman
J W
JW
Cooper
J M
JM
Nelson
I
I
Hargreaves
I
I
Meunier
B
B
Hanna
M G
MG
García
J J
JJ
Capaldi
R A
RA
Lake
B D
BD
Leonard
J V
JV
Schapira
A H
AH
D000140:Acidosis, Lactic / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000293:Adolescent; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D002467:Cell Nucleus / Q000201:enzymology; D019069:Cell Respiration; D002478:Cells, Cultured; D030401:Cytochrome-c Oxidase Deficiency; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004795:Enzyme Stability; D006418:Heme / Q000031:analogs & derivatives* / Q000378:metabolism; D020035:Holoenzymes / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense / Q000235:genetics*; D010782:Photolysis; D011048:Polarography; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment
D004272:DNA, Mitochondrial; D020035:Holoenzymes; C027728:heme a; D006418:Heme; C117108:cytochrome C oxidase subunit II; D003576:Electron Transport Complex IV