Detergent modulation of electron and proton transfer reactions in bovine cytochrome c oxidase

The effect of detergents on electron and proton transfer in bovine cytochrome c oxidase was studied using steady-state and transient-state methods. Cytochrome c oxidase in lauryl maltoside has high maximal turnover (TNmax = 400 s(-1)), whereas activity is low (TNmax = 10 s(-1)) in Triton X-100. Single turnover studies of intramolecular electron transfer show similar rates in either detergent. Transient proton uptake experiments show the oxidase in lauryl maltoside consumes 1.8 +/- 0.3 H+/aa(3) during either partial reduction of the oxidase or reaction of fully reduced enzyme with 0,. However. the oxidase in Triton X-100 consumes 2.6 +/- 0.4 H+/aa(3) during partial reduction and 1.0 +/- 0.2 H+/aa(3) in the O-2 reaction. Absorption spectra recorded during turnover show that the enzyme undergoes activation in lauryl maltoside, but does not activate in Triton X-100. We propose that cytochrome c oxidase in different detergents allows access to different sites of protonation, which in turn influences steady-state activity. (C) 2002 Elsevier Science (USA). All rights reserved.