Towards a Rational Control of the Electronic Structure of Electron Transfer Metalloproteins

ESPINOZA CARA, AM; LEGUTO, AJ; LLASES, ME; MORGADA, MN; VILA, AJ

Villa Carlos Paz

Conferencia; Conferencia; 13ª Conferencia Latinoamericana de Fisicoquímica Orgánica; 2015; 2015

CLAFQO13

The dinuclear copper center CuA is theelectron entry point of cytochrome coxidase (COX). CuA funnels the electrons from reduced cytochrome c to the CuB center atsubunit I of COX where O2 is reduced to water molecules. Theseelectron transfer reactions are highly efficient and this efficiency is givenby the characteristic coordination chemistry of this center.Two alternative electronic ground levels, withdifferent orbital symmetries, have been established for the CuA center in itsoxidized form (Cu+1.5-Cu+1.5) σμ* and πμ.NMR studies of COX II from Thermusthermophilus (Tt-COX II) revealedthe presence of signals with Non-Curie temperature dependence behavior,indicating that these levels are very close in energy, and both can bepopulated at room temperature. However σμ* has been considered asthe only redox active.Studies made with mutants of the first coordinationsphere of the CuA site in Tt-COXII, showed that the energy gap between these two electronic levels can be finetuned and mutations that cause an increase in the population of the πμstate are not detrimental in the electron transfer process, demonstrating thatπμ state is also redox active in the electron transfer process.1Recently we also found that mutations in the secondcoordination sphere also tune the energy gap between the σμ* and πμstates by replacing the loops surrounding the metal site in Tt-COX II by the ones present in aneukaryotic homologue, COX II*.2 Here we will show that firstcoordination sphere mutations on COX II* tune the electronic structure of theCuA site in the same direction as in Tt-COXII.