Crystallization of mitochondrial ubiquinol-cytochrome c reductase.

Ubiquinol−cytochrome c reductase of beef heart mitochondria was crystallized in the presence of decanoyl-N-methylglucamide, heptanetriol, and sodium chloride with poly(ethylene glycol) as precipitant. The largest crystal has dimensions of 4×2×1 mm. The crystalline enzyme is composed of 10 subunits. It contains 2.5 nmol of ubiquinone, 8.4 nmol of cytochrome b, 4.2 nmol of cytochrome c 1 , 4.2 nmol of iron−sulfur cluster, and 140 nmol of phospholipid per milligram of protein. Of the last, 36% is with diphosphatidylglycerol. The crystals are very stable in the cold and show full enzymatic activity when redissolved in aqueous solution