Distribution of the ATPase inhibitor proteins of mitochondria in mammalian tissues including fibroblasts from a patient with Luft's disease.

The mitochondrial ATPase inhibitor proteins--the Pullman-Monroy inhibitor (PMI) and the Ca(2+)-binding protein (CaBI)--have a wide distribution, both being present in mitochondria of bovine heart and kidney, rat liver and brain, two mitochondrial populations of rabbit skeletal muscle, and mitochondria from human fibroblasts and the human breast cancer cell line T-47-D. The ratio of CaBI to PMI was highest in heart and skeletal muscle mitochondria. The subsarcolemmal fraction of skeletal muscle had 2.6-times as much CaBI as did the intermyofibrillar. The ratio of CaBI to PMI in the mitochondria of the other normal tissues and fibroblasts was close to 1. In contrast, mitochondria from T-47D cells had 1.5-times as much PMI as CaBI whilst mitochondria from fibroblasts from a patient with Luft's disease showed a virtual lack of PMI. The specific ATPase, ATP-synthetase and succinate dehydrogenase activities of the Luft's mitochondria were, however, in the normal range. The specific ATP synthetase activity of the T-47D cells was significantly higher than normal. We conclude that tissues like heart and skeletal muscle which experience wide fluctuations in intracellular Ca2+ have a greater need for CaBI. Why lack of PMI could lead to 'loose' coupling of oxidative phosphorylation in skeletal muscle of Luft's patients, but not in fibroblasts is discussed.