Tunneling and Nonadiabatic Effects on a Proton-Coupled Electron Transfer Model for the Q(0) Site in Cytochrome bc(1)

Autor(es)

Camilo, Sofia R. G. ; Curtolo, Felipe ; Galassi, Vanesa V. ; Arantes, Guilherme M.

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF CHEMICAL INFORMATION AND MODELING; v. 61, n. 4, p. 10-pg., 2021-04-01.

Resumo

Cytochrome bc(1) is a fundamental enzyme for cellular respiration and photosynthesis. This dimeric protein complex catalyzes a proton-coupled electron transfer (PCET) from the reduced coenzyme-Qsubstrate (Q) to a bimetallic iron- sulfur cluster in the Q active site. Herein, we combine molecular dynamics simulations of the complete cytochrome bc(1) protein with electronic-structure calculations of truncated models and a semiclassical tunneling theory to investigate the electron-proton adiabaticity of the initial reaction catalyzed in the Q site. After sampling possible orientations between the Q substrate and a histidine side chain that functions as hydrogen acceptor, we find that a truncated model composed by ubiquinol-methyl and imidazole-iron(III)-sulfide captures the expected changes in oxidation and spin states of the electron donor and acceptor. Diabatic electronic surfaces obtained for this model with multiconfigurational wave function calculations demonstrate that this reaction is electronic nonadiabatic, and proton tunneling is faster than mixing of electronic configurations. These results indicate the formalism that should be used to calculate vibronic couplings and kinetic parameters for the initial reaction in the Q(0) site of cytochrome bc(1). This framework for molecular simulation may also be applied to investigate other PCET reactions in the Qcycle or in various metalloproteins that catalyze proton translocation coupled to redox processes. (AU)

• Processo FAPESP: 17/26109-0 - Simulação computacional de reatividade e transferência de elétrons no complexo II respiratório
• Beneficiário: Felipe Curtolo
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 19/05531-0 - Simulação computacional da ligação e da reatividade de substrato coenzima-Q no complexo respiratório III
• Beneficiário: Sofia Rodrigues Guedes Camilo
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 12/17833-2 - Simulações computacionais de citocromo bc1 e de Cdc25B fosfatase com validação espectroscópica
• Beneficiário: Vanesa Viviana Galassi
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 19/21856-7 - Bioenergética molecular computacional
• Beneficiário: Guilherme Menegon Arantes
• Modalidade de apoio: Auxílio à Pesquisa - Regular