title: Structural dynamics of myoglobin: an infrared kinetic study of ligand migration in mutants YQR and YQRF.
abstract: Recombination of carbon monoxide to myoglobin mutants YQR and YQRF was studied using transient infrared absorption spectroscopy and Fourier transform infrared-temperature derivative spectroscopy (FTIR-TDS). Photoproduct states B, C', C" and D associated with ligands residing in different protein cavities have been identified. After photolysis, ligands migrate to primary docking site B and subsequently rebind or escape to a secondary site (C) within the Xe4 cavity. For YQR, a global analysis of the isothermal rebinding kinetics below 160 K and the TDS data reveal a correlation between the enthalpy barriers governing the two processes. Above 120 K, a protein conformational change in both YQR and YQRF converts photoproduct C' into C" with markedly slowed kinetics. Above approximately 180 K, ligands migrate to the proximal Xe1 site (D) and also exit into the solvent, from where they rebind in a bimolecular reaction.
authors.affiliation: Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Don C
authors.initials: DC
authors.lastname: Lamb
authors.forename: Alessandro
authors.initials: A
authors.lastname: Arcovito
authors.forename: Karin
authors.initials: K
authors.lastname: Nienhaus
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Minkow
authors.forename: Federica
authors.initials: F
authors.lastname: Draghi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
authors.forename: G Ulrich
authors.initials: GU
authors.lastname: Nienhaus
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008962:Models, Theoretical; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013816:Thermodynamics
chemical_list: D008024:Ligands; D009211:Myoglobin; D002248:Carbon Monoxide