Keigo Nishikawa

Electronic and geometric structures of the blue copper site of azurin investigated by QM/MM hybrid calculations

The electronic and geometric structures of the copper-binding site in a fully solvated azurin were investigated using quantum mechanics (QM) and molecular mechanics (MM) hybrid calculations. Two types of computational models were applied to evaluate the effects of the environment surrounding the active site. In model I, long-distance electrostatic interactions between QM region atoms and partial point charges of the surrounding protein moieties and solvent water were calculated in a QM Hamiltonian, for which the spin-unrestricted Hartree-Fock (UHF)/density functional theory (DFT) hybrid all-electron calculation with the B3LYP functional was adopted. In model II, the QM Hamiltonian was not allowed to be polarized by those partial point charges. Models I and II provided different descriptions of the copper coordination structure, particularly for the coordinative bonds including a large dipole. In fact, the Cu-O(Gly45) and Cu-S(Cys112) bonds are sensitive to the treatment of long-distance electrostatic interactions in the QM Hamiltonian. This suggests that biological processes occurring in the active site are regulated by the surrounding structures of protein and solvent, and therefore the effects of long-range electrostatic interactions involved in the QM Hamiltonian are crucial for accurate descriptions of electronic structures of the copper active site of metalloenzymes.

Theoretical Studies on Docking Dynamics and Electronic Structure in Metalloprotein Complexes

An investigating of docking structure and dynamics between metalloprotein is interested from the viewpoint of searching the function of protein. We investigate the cytochrome c551 and azurin complexes by three computational methods, quantum mechanical calculation, docking searching algorism and molecular dynamics simulation. At first we present the docking structure of the cytochrome c551‐azurin complexes expected by ZDOCK searching algorism. Quantum chemical calculation is tools to estimate the charge distrubution around the active site for each protein and force field parameters. From these parameters, we reproduce the protein docking dynamics by molecular dynamics simulation. We analyze some physical properties of complex system such as binding free energy, dynamical cross correlation map, and so on. We discuss the docking stability and dynamical effect of the cytochrome c551‐azurin complexes.

Free Energy Calculation of Docking Structure of Azurin(I)‐Cytochrome c551(III) Complex Systems by Using the Energetic Representation

We investigate the docking stability of Azurin(I)—Cytochrome C551(III) complex by molecular dynamic simulations. The charge distribution around the active sites for Azurin(I) and Cytochrome C551(III) is estimated by quantum chemical calculation to simulate the complex system by molecular dynamic simulations. We estimete some physical properties such as the root square mean deviation, distance between iron ion in active site of Cytochrome C551(III) and copper ion in active site of Azurin(I), the dynamical cross‐correlation map and free energy in the energetic representation. We discuss the stability of the complex system of Azurin(I)—Cytochrome C551(III) from these properties.

Theoretical Study of Free Energy in Docking Stability of Azurin(II)‐Cytochrome c551(II) Complex System

The docking structure of the Azurin‐Cytochrome C551 is presented. We investigate a complex system of Azurin(II)‐Cytochrome C551(II) by using molecular dynamics simulation. We estimate some physical properties, such as root‐mean‐square deviation (RMSD), binding energy between Azurin and Cytochrome C551, distance between Azurin(II) and Cytochrome C551(II) through center of mass and each active site. We also discuss docking stability in relation to the configuration by free energy between Azurin(II)‐Cytochrome C551(II) and Azurin(I)‐Cytochrome C551(III).