Functional binding of cardiolipin to cytochromec oxidase

Abstract

Bovine cytochromec oxidase usually contains 3–4 mol of tightly bound cardiolipin per cytochromeaa ₃ complex. At least two of these cardiolipins are required for full electron transport activity. Without the tightly bound cardiolipin, cytochromec oxidase has only 40–50% of its original activity when assayed in detergents that support activity, e.g., dodecyl maltoside. By measuring the restoration of electron transport activity, functional binding constants for cardiolipin and a number of cardiolipin analogues have been evaluated (K _d,app=1 µM for cardiolipin). These binding constants agree reasonably well with direct measurement of the binding using [¹⁴C]-acetyl-cardiolipin (K _d c oxidase and the other mitochrondrial electron transport complexes and transporters.