Isolation of the Cytochrome‐bc1 Complex from Rat‐Liver Mitochondria

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Abstract
The cytochrome bc1 complex was isolated from rat-liver mitochondria by 2 different procedures. The enzyme isolated by either procedure exhibits a specific cytochrome b and cytochrome c1 heme content of .apprx. 8 and 4 nmol/mg protein, respectively. Both preparations contain only 7 polypeptides on sodium dodecylsulfate gel electrophoresis, with the following apparent MW: I, 50,000; II, 46,000; III, 33,000; IV, 25,000; V, 12,500; VI, 10,000; VII, 5600. The polypeptide composition is identical to that of the beef-heart enzyme isolated by cholate/ammonium sulfate fractionation. With the exception of subunit II (core protein 2), the apparent MW of the subunits are identical in the rat-liver and beef-heart enzymes.