Artículos de revistas
Electrostatically Driven Second-Sphere Ligand Switch between High and Low Reorganization Energy Forms of Native Cytochrome c
Fecha
2013-03Registro en:
Álvarez Paggi, Damián Jorge; Castro, Maria Ana; Tortora, Verónica; Castro, Laura; Radi, Rafael; et al.; Electrostatically Driven Second-Sphere Ligand Switch between High and Low Reorganization Energy Forms of Native Cytochrome c; Amer Chemical Soc; Journal of the American Chemical Society; 135; 3-2013; 4389-4397
0002-7863
Autor
Álvarez Paggi, Damián Jorge
Castro, Maria Ana
Tortora, Verónica
Castro, Laura
Radi, Rafael
Murgida, Daniel Horacio
Resumen
We have employed a combination of protein film voltammetry, time-resolved vibrational spectroelectrochemistry and molecular dynamics simulations to evaluate the electron-transfer reorganization free energy (λ) of cytochrome c (Cyt) in electrostatic complexes that mimic some basic features of protein–protein and protein–lipid interactions. The results reveal the existence of two native-like conformations of Cyt that present significantly different λ values. Conversion from the high to the low λ forms is triggered by electrostatic interactions, and involves the rupture of a weak H-bond between first- (M80) and second-sphere (Y67) ligands of the heme iron, as a distinctive feature of the conformational switch. The two flexible Ω loops operate as transducers of the electrostatic signal. This fine-tuning effect is abolished in the Y67F Cyt mutant, which presents a λ value similar to the WT protein in electrostatic complexes. We propose that interactions of Cyt with the natural redox partner proteins activate a similar mechanism to minimize the reorganization energy of interprotein electron transfer.