ИСТИНА

A soluble protein fraction, which confers the reactivity of soluble succinate dehydrogenase towards ubiquinone, was isolated from beef heart mitochondria. This fraction contains three polypeptides as revealed by SDS-electrophoresis; the major peptide (about 80% of protein) has a molecular weight less than 13 000. Several properties of the reconstituted succinate-ubiquinone reductase, i. e. the turnover number of succinate dehydrogenase inhibitor sensitivity, stability and reactivity towards artificial electron acceptors were found to be identical to those of the native succinate-ubiquinone region of the respiratory chain. A model of the minimal functionally active structure capable of reduction of ubiquinone by succinate is proposed.