Analyses of muscle proteins in a patient with a mitochondrial myopathy.

Using the small amounts of muscle available from biopsy (approximately 100 mg), from both normal controls and a patient with a previously identified defect of the mitochondrial electron transfer protein complex III, we analyzed both structural and mitochondrial proteins. The myosin light chains were found to be unchanged with respect to charge or size between patient and control. Two prominent proteins detected after two dimensional gel electrophoresis were present in the patient's total homogenised muscle protein but were not detected in the controls. One protein was positively identified as cytochrome c oxidase subunit II and the other tentatively as a component of the ATP synthetase. We suggest that the increased amounts of these proteins represents a response of the patients muscle cells to the ATP deficiency caused by the primary lesion in complex III.