Design Parameters for Tuning the Type 1 Cu Multicopper Oxidase Redox Potential: Insight from a Combination of First Principles and Empirical Molecular Dynamics Simulations

Abstract

The redox potentials and reorganization energies of the type 1 (T1) Cu site in four multicopper oxidases were calculated by combining first principles density functional theory (QM) and QM/MM molecular dynamics (MD) simulations. The model enzymes selected included the laccase from Trametes versicolor, the laccase-like enzyme isolated from Bacillus subtilis, CueO required for copper homeostasis in Escherichia coli, and the small laccase (SLAC) from Streptomyces coelicolor. The results demonstrated good agreement with experimental data and provided insight into the parameters that influence the T1 redox potential. Effects of the immediate T1 Cu site environment, including the His(N(δ))-Cys(S)-His(N(δ)) and the axial coordinating amino acid, as well as the proximate H(N)(backbone)-S(Cys) hydrogen bond, were discerned. Furthermore, effects of the protein backbone and side-chains, as well as of the aqueous solvent, were studied by QM/MM molecular dynamics (MD) simulations, providing an understanding of influences beyond the T1 Cu coordination sphere. Suggestions were made regarding an increase of the T1 redox potential in SLAC, i.e., of Met198 and Thr232 in addition to the axial amino acid Met298. Finally, the results of this work presented a framework for understanding parameters that influence the Type 1 Cu MCO redox potential, useful for an ever-growing range of laccase-based applications.

Laccase Redox Potentials: pH Dependence and Mutants, a QM/MM Study

“…The stepwise changes in redox potential during O 2 activation and effects of groups close to the redox centres have been studied on a quantum chemical level. 4,7,8 A recent article even the one reducing O 2 ( Figure 1). 11 T1 centres are found in several (non-MCO) enzymes not featuring a TNC, 12 for example in plastocyanin.…”

Biohydrogen for a New Generation of H2/O2 Biofuel Cells: A Sustainable Energy Perspective

“…In BOD, values between + 0.4 and + 0.5 V vs. Ag/AgCl are reported, thus they are somehow lower than observed in high potential LACs. [54][55][56][57] The variation in the potential values depends on the Cu coordination, nature of the ligands, geometry of the T1 Cu center, and the electrostatic and solvent effects. Potential values for T2 and T3 centers are more difficult to evaluate because of the many intermediates with different geometries and oxidation states that are generated in the course of O 2 reduction.…”

On the Possibility of Uphill Intramolecular Electron Transfer in Multicopper Oxidases: Electrochemical and Quantum Chemical Study of Bilirubin Oxidase

“…Moreover, QM/MM molecular dynamics simulations have been used to calculate the E T1 and λ values of the Cu-T1 site in different MCO [54]. These studies clearly demonstrated that Buffers were prepared with water (18 MΩ·cm) purified with a PURELAB UHQ II system from ELGA Labwater (High Wycombe, UK).…”