Analyzing your complexes: structure of the quinol-fumarate reductase respiratory complex

The integral membrane protein complex quinol-fumarate reductase catalyzes t he terminal step of a major anaerobic respiratory pathway. The homologous e nzyme succinate-quinone oxidoreductase participates in aerobic respiration both as complex II and as a member of the Krebs cycle. Last year, two struc tures of quinol-fumarate reductases were reported. These structures reveale d the cofactor organization linking the fumarate and quinol sites, and show ed a cofactor arrangement across the membrane that is suggestive of a possi ble energy coupling function.