title: Reversible Switching of Redox-Active Molecular Orbitals and Electron Transfer Pathways in Cu(A) Sites of Cytochrome c Oxidase.
abstract: The Cu(A) site of cytochrome c oxidase is a redox hub that participates in rapid electron transfer at low driving forces with two redox cofactors in nearly perpendicular orientations. Spectroscopic and electrochemical characterizations performed on first and second-sphere mutants have allowed us to experimentally detect the reversible switching between two alternative electronic states that confer different directionalities to the redox reaction. Specifically, the M160H variant of a native Cu(A) shows a reversible pH transition that allows to functionally probe both states in the same protein species. Alternation between states exerts a dramatic impact on the kinetic redox parameters, thereby suggesting this effect as the mechanism underlying the efficiency and directionality of Cu(A) electron transfer in vivo. These findings may also prove useful for the development of molecular electronics.
authors.affiliation: Instituto de Química Física de los Materiales, Medio Ambiente y Energía, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET (Argentina).
authors.forename: Ulises
authors.initials: U
authors.lastname: Zitare
authors.affiliation: Instituto de Química Física de los Materiales, Medio Ambiente y Energía, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET (Argentina).
authors.forename: Damián
authors.initials: D
authors.lastname: Alvarez-Paggi
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), Departamento de Química Biológica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and CONICET (Argentina).
authors.forename: Marcos N
authors.initials: MN
authors.lastname: Morgada
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), Departamento de Química Biológica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and CONICET (Argentina).
authors.forename: Luciano A
authors.initials: LA
authors.lastname: Abriata
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR), Departamento de Química Biológica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and CONICET (Argentina).
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Vila
authors.affiliation: Instituto de Química Física de los Materiales, Medio Ambiente y Energía, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET (Argentina). dhmurgida@qi.fcen.uba.ar.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Murgida
mesh_terms: D003300:Copper / Q000737:chemistry*; D003573:Cytochrome b Group / Q000737:chemistry*; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry*; D004583:Electrons; D010084:Oxidation-Reduction; D016963:Thermus thermophilus / Q000737:chemistry / Q000201:enzymology*
chemical_list: D003573:Cytochrome b Group; D003300:Copper; C058557:cytochrome ba3; D003576:Electron Transport Complex IV
keywords: cytochrome c oxidase; electrochemistry; electron transfer; electronic structures; enzymes