Schapira et al. (1990) described the 14-year-old daughter of an English father and Chinese mother who had had muscle weakness and exercise intolerance since early infancy. Fetal movements had been reduced during pregnancy. There were no clinical manifestations related to systems other than skeletal muscle. Deficiency of respiratory-chain Complexes I to IV was found. Mitochondrial preparations showed specific deficiencies of both the iron-sulfur protein of Complex III ('Rieske' protein) and the 27.2-kD subunit of succinate dehydrogenase. Similar experiments with muscle homogenates indicated a deficiency of the subunit of succinate dehydrogenase, but normal levels of the precursor Rieske protein. The findings were interpreted as indicating a defect in the transport of the Rieske protein into mitochondria. Schapira et al. (1990) speculated that some iron-sulfur proteins of the mitochondrial respiratory chain may be encoded by a cluster of nuclear genes and that a mutation affecting a single coding sequence could account for the double deficiency. This could lead to a reduced synthesis of the 27.2-kD polypeptide and produce changes in the coding of the Rieske precursor sequence such that its receptor-mediated transport into mitochondria is defective.
Schapira, A. H. V., Cooper, J. M., Morgan-Hughes, J. A., Landon, D. N., Clark, J. B. Mitochondrial myopathy with a defect of mitochondrial-protein transport. New Eng. J. Med. 323: 37-42, 1990. [PubMed: 2113185] [Full Text: https://doi.org/10.1056/NEJM199007053230107]