A proton NMR study of the electron exchange between reduced and oxidized azurin from Pseudomonas aeruginosa

Abstract

The line broadening observed at 50C in the proton NMR spectrum of a partly oxidized solution of azurin from Pseudomonas aeruginosa is consistent with assignments of peaks belonging to the ligand residues His-46, His-117, and Met-121 of the copper atom. From the analysis of the tine broadening a value of k = 2 × 10 6 M − sec −1 is obtained for the bimolecular rate constant of the electron self-exchange reaction of azurin at 50°C. The analysis also provides insight into the spin density distribution over the Cu ligands in oxidized azurin. Finally the data show that small configurational changes in the vicinity of Val-31 occur upon oxidation of the protein.