Electron transfer dynamics of Rhodothermus marinus caa3 cytochrome c domains on biomimetic films

MOLINAS, M.F.; DE CANDIA, A.; SZAJNMAN, S.H.; RODRÍGUEZ, J.B.; MARTÍ, M.; PEREIRA, M. M.; TEIXEIRA, M.; TODOROVIC, S.; MURGIDA, D.H.

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2011 vol. 13 p. 18088 - 18098

1463-9076

The subunit II of the caa3 oxygen reductase from Rhodothermus marinus contains, in addition to the CuA center, a c-type heme group in the cytochrome c domain (Cyt-D) that is the putative primary electron acceptor of the enzyme. In this work we have combined surface-enhanced resonance Raman (SERR) spectroelectrochemistry, molecular dynamics (MD) simulations and electron pathway calculations to assess the most likely interaction domains and electron entry/exit points of the truncated Cyt-D of subunit II in the reactions with its electron donor,HiPIP and electron acceptor, CuA. The results indicate that the transient interaction between Cyt-D and HiPIP relies upon a delicate balance of hydrophobic and polar contacts for establishing an optimized electron transfer pathway that involves the exposed edge of the heme group and guaranties efficient inter-protein electron transfer on the nanosecond time scale. The reorganization energy of ca. 0.7 eV was determined by time-resolved SERR spectroelectrochemistry. The intramolecular electron transfer pathway in integral subunit II from Cyt-D to the CuA redox center most likely involves the iron ligand histidine 20 as an electron exit point in Cyt-D.