A missense mutation of cytochrome oxidase subunit II causes defective assembly and myopathy.
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Rahman S, Taanman JW, Cooper JM, Nelson I, Hargreaves I, Meunier B, Hanna MG, Garcia JJ, Capaldi RA, Lake BD, Leonard JV, Schapira AH
A missense mutation of cytochrome oxidase subunit II causes defective assembly and myopathy.
Am J Hum Genet. 1999 Oct;65(4):1030-9.
- PubMed ID
- 10486321 [ View in PubMed]
- Abstract
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.