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 (TN(max)=400 s(-1)), whereas activity is low (TN(max)=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 O(2). 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.
Tarasev
Michael
M
Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-0606, USA.
Hill
Bruce C
BC
D000818:Animals; D002384:Catalysis; D002417:Cattle; D003902:Detergents / Q000737:chemistry* / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects / Q000502:physiology*; D003576:Electron Transport Complex IV / Q000737:chemistry*; D005960:Glucosides / Q000737:chemistry / Q000494:pharmacology; D017830:Octoxynol / Q000737:chemistry / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010100:Oxygen / Q000737:chemistry; D010782:Photolysis; D011487:Protein Conformation / Q000187:drug effects; D011522:Protons; D013053:Spectrophotometry
D003902:Detergents; D005960:Glucosides; D011522:Protons; C040358:dodecyl maltoside; D017830:Octoxynol; D003576:Electron Transport Complex IV; D010100:Oxygen