Redesigned CuA site shows degenerate alternative ground - states

ZITARE, U; LANCASTER, KM; LEGUTO, AJ; MORGADA, MN; VILA, AJ; SMITH, MA; MURGIDA, DH

Querétaro

Congreso; V LABIC; 2016

CONACYT - CINVESTAV

 CuA is a binuclearcopper center that participates in highly efficient electron-transfer processes1.In the oxidized state, CuA center is a mixed valence pair. Itselectronic structure which can be described by two alternative ground-states: su* and πuground-state. The πu ground-state has higher energy and is partiallypopulated at room temperature, rapidly interconverting with su*.2Moreover, replacing a native Met axial copper ligand, redox potential and su*/πuenergy gap can be tuned: it decreases from 600cm-1 in WT protein to 200cm-1in a M160H mutant.3 Recently, the Tt3L chimeric protein was created replacing three loops surroundingCuA by their eukaryotic homologous, thus only incorporating second-sphereperturbations.4 This chimera also shows a decrease in the su*/πuenergy-gap to 240cm-1. Herein we report the characterization of amutant in which we combine first- and second-sphere mutations (Tt3L-M160H) which is characterized bytwo degenerate su*/πulevels, showing that these mutations have additive effects on the electronicstructure. These changes are not reflected in severe perturbations on the Cu-Cudistance.