Fine Tuning of the Electronic Structure of the CuA Site by Second Sphere Perturbations: Implications for Electron Transfer in Heme-Copper Oxidases

MORGADA M.; ABRIATA, L.A.; ZITARE U.; ALVAREZ PAGGI, D.; MURGIDA D.H.; VILA, A. J.

ANGEWANDTE CHEMIE

VCH PUBLISHERS INC

Lugar: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim; Año: 2014 vol. 53 p. 6188 - 6192

0570-0833

CuA center is a dinuclear copper site which acts as an optimized hub for long-range electron transfer in terminal oxidases. Its electronic structure can be described by a σu* ground state wavefunction, despite an alternative ground state of πu symmetry is also thermally accessible. Here we show that second-sphere mutations in an engineered variant of the CuA-containing subunit of Thermus thermophilus ba3 oxidase perturb the electronic structure by changing the relative population of the σu* and πu states, as shown by UV-Vis, EPR and NMR spectroscopies. Electrochemical studies show that this perturbation does not affect the redox potential of the metal site and preserves the electron transfer features. These perturbations were achieved by replacing the loops involved in interprotein interaction with cytochrome c, suggesting that transient protein binding could also elicit ground state switching in the oxidase.