title: Binding of ligands originates small perturbations on the microscopic thermodynamic properties of a multicentre redox protein.
abstract: NMR and visible spectroscopy coupled to redox measurements were used to determine the equilibrium thermodynamic properties of the four haems in cytochrome c3 under conditions in which the protein was bound to ligands, the small anion phosphate and the protein rubredoxin with the iron in the active site replaced by zinc. Comparison of these results with data for the isolated cytochrome shows that binding of ligands causes only small changes in the reduction potentials of the haems and their pairwise interactions, and also that the redox-sensitive acid-base centre responsible for the redox-Bohr effect is essentially unaffected. Although neither of the ligands tested is a physiological partner of cytochrome c3, the small changes observed for the thermodynamic properties of cytochrome c3 bound to these ligands vs. the unbound state, indicate that the thermodynamic properties measured for the isolated protein are relevant for a physiological interpretation of the role of this cytochrome in the bioenergetic metabolism of Desulfovibrio.
authors.affiliation: Instituto de Tecnologia Quimica e Biológica, Universidade Nova de Lisboa, Portugal.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Salgueiro
authors.forename: Leonor
authors.initials: L
authors.lastname: Morgado
authors.forename: Bruno
authors.initials: B
authors.lastname: Fonseca
authors.forename: Pedro
authors.initials: P
authors.lastname: Lamosa
authors.forename: Teresa
authors.initials: T
authors.lastname: Catarino
authors.forename: David L
authors.initials: DL
authors.lastname: Turner
authors.forename: Ricardo O
authors.initials: RO
authors.lastname: Louro
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D003574:Cytochrome c Group / Q000737:chemistry*; D016969:Desulfovibrio vulgaris / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D011485:Protein Binding; D012416:Rubredoxins / Q000737:chemistry; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D008024:Ligands; D012416:Rubredoxins; D006418:Heme; C017165:cytochrome c(3); D015032:Zinc