title: Titration behavior of residues at the entrance of the D-pathway of cytochrome c oxidase from paracoccus denitrificans investigated by continuum electrostatic calculations.
abstract: Continuum electrostatic calculations were employed to investigate the titration curves of the fully oxidized state of wild type and several variants of cytochrome c oxidase from Paracoccus denitrificans (N131D, N131C, N131V, and D124N) for different values of the dielectric constant of the protein. The effects of the mutations at the entrance of the D-proton transfer pathway were found to be quite localized to their immediate surroundings. The results can be well interpreted in the light of the available biochemical and structural data and help understanding the effects of mutations on proton conductivity. The mutations of aspartic acid Asp-I-124 to a neutral residue resulted in a decreased pK(a) value of His-I-28 suggesting that the mutation of His-I-28 may have a significant influence on the coupling of electron and proton transfer in cytochrome c oxidase. We also investigated the effect of the mutations N131D, N131C, and N131V on the residue Glu-I-278 in terms of its pK(a) value and electrostatic interaction energies.
authors.affiliation: Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, D-60438 Frankfurt, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Olkhova
authors.forename: Volkhard
authors.initials: V
authors.lastname: Helms
authors.forename: Hartmut
authors.initials: H
authors.lastname: Michel
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry; D001693:Biological Transport, Active; D003198:Computer Simulation; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D009038:Motion; D009154:Mutation; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011487:Protein Conformation; D017494:Proton Pumps / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D055672:Static Electricity; D013329:Structure-Activity Relationship; D017186:Titrimetry
chemical_list: D000596:Amino Acids; D017494:Proton Pumps; D011522:Protons; D003576:Electron Transport Complex IV