Role of protein frame and solvent for the redox properties of azurin from Pseudomonas aeruginosa.
We have coupled hybrid quantum mechanics (density functional theory; Car-Parrinello)/molecular mechanics molecular dynamics simulations to a grand-canonical scheme, to calculate the in situ redox potential of the Cu(2+) + e(-) --> Cu(+) half reaction in azurin from Pseudomonas aeruginosa. An accurate description at atomistic level of the environment surrounding the metal-binding site and finite-temperature fluctuations of the protein structure are both essential for a correct quantitative description of the electronic properties of this system. We report a redox potential shift with respect to copper in water of 0.2 eV (experimental 0.16 eV) and a reorganization free energy lambda = 0.76 eV (experimental 0.6-0.8 eV). The electrostatic field of the protein plays a crucial role in fine tuning the redox potential and determining the structure of the solvent. The inner-sphere contribution to the reorganization energy is negligible. The overall small value is mainly due to solvent rearrangement at the protein surface.
Cascella
Michele
M
Ecole Polytechnique Fédérale de Lausanne, Laboratory of Computational Chemistry and Biochemistry, 1015 Lausanne, Switzerland.
Magistrato
Alessandra
A
Tavernelli
Ivano
I
Carloni
Paolo
P
Rothlisberger
Ursula
U
D001400:Azurin / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D019295:Computational Biology; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000378:metabolism*; D012997:Solvents; D055672:Static Electricity
D012997:Solvents; D001400:Azurin; D003300:Copper