Electron tunneling in respiratory complex I.
NADH:ubiquinone oxidoreductase (complex I) plays a central role in the respiratory electron transport chain by coupling the transfer of electrons from NADH to ubiquinone to the creation of the proton gradient across the membrane necessary for ATP synthesis. Here the atomistic details of electronic wiring of all Fe/S clusters in complex I are revealed by using the tunneling current theory and computer simulations; both density functional theory and semiempirical electronic structure methods were used to examine antiferromagnetically coupled spin states and corresponding tunneling wave functions. Distinct electron tunneling pathways between neighboring Fe/S clusters are identified; the pathways primarily consist of two cysteine ligands and one additional key residue. Internal water between protein subunits is identified as an essential mediator enhancing the overall electron transfer rate by almost three orders of magnitude to achieve a physiologically significant value. The identified key residues are further characterized by sensitivity of electron transfer rates to their mutations, examined in simulations, and their conservation among complex I homologues. The unusual electronic structure properties of Fe(4)S(4) clusters in complex I explain their remarkable efficiency of electron transfer.
Department of Chemistry, University of California, Davis, CA 95616, USA.
Tomoyuki
T
Hayashi
Alexei A
AA
Stuchebrukhov
D003198:Computer Simulation; D004579:Electron Transport; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000235:genetics; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation
D007506:Iron-Sulfur Proteins; D042967:Electron Transport Complex I