title: Ligand-induced tertiary relaxations during the T-to-R quaternary transition in hemoglobin.
abstract: When human hemoglobin is encapsulated in nanoporous silica gels, tertiary and quaternary structural relaxations are dramatically slowed down, allowing the characterization of elusive reaction intermediates. In this work, the conformational and functional changes triggered by CO binding to human deoxyhemoglobin gels were determined in the absence and presence of allosteric effectors. CO rebinding kinetics to human deoxyhemoglobin gels after nanosecond laser photolysis were monitored as a function of time after CO saturation. A maximum entropy analysis of the CO rebinding kinetics shows that the T conformation slowly evolves toward R, with an associated redistribution of tertiary species. The tertiary species are characterized by different CO rebinding rates which are essentially unaffected by the protein quaternary state.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Universita degli Studi di Parma, CNISM.
authors.forename: Luca
authors.initials: L
authors.lastname: Ronda
authors.forename: Stefania
authors.initials: S
authors.lastname: Abbruzzetti
authors.forename: Stefano
authors.initials: S
authors.lastname: Bruno
authors.forename: Stefano
authors.initials: S
authors.lastname: Bettati
authors.forename: Andrea
authors.initials: A
authors.lastname: Mozzarelli
authors.forename: Cristiano
authors.initials: C
authors.lastname: Viappiani
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D006454:Hemoglobins; D008024:Ligands; D002248:Carbon Monoxide