Abstract
Cardiolipin (CL) is a lipid that is found in the membranes of bacteria and the inner membranes of mitochondria. CL can increase the activity of integral membrane proteins, in particular components of respiratory pathways. We here report that CL activated detergent-solubilized cytochrome bd, a terminal oxidase from Escherichia coli. CL enhanced the oxygen consumption activity similar to twofold and decreased the apparent K-M value for ubiquinol-1 as substrate from 95 mu M to 35 mu M. Activation by CL was also observed for cytochrome bd from two Gram-positive species, Geobacillus thermodenitrificans and Corynebacterium glutamicum, and for cytochrome bo(3) from E. coli. Taken together, CL can enhance the activity of detergent-solubilized cytochrome bd and cytochrome bo(3).