title: Direct evidence for the role of haem doming as the primary event in the cooperative transition of haemoglobin.
abstract: The study of cooperative ligand binding among the four subunits of haemoglobin has played a central role in the understanding of allosteric transitions in a large number of enzymes. Haem iron out-of-plane motion has been suggested to be the trigger for the cooperative transition of haemoglobin. To function as a trigger in a dynamic sense, haem-iron doming must be the first conformational change to occur following ligand dissociation. Here we present the first direct demonstration that haem-iron doming occurs on the same time scale as the breaking of the iron-ligand bond, thus establishing haem-iron doming as the primary event which lead to the R-->T transition in haemoglobin.
authors.affiliation: Laboratoire d'Optique Appliquée INSERM U275, Ecole Polytechnique-ENSTA, Palaiseau, France.
authors.forename: S
authors.initials: S
authors.lastname: Franzen
authors.forename: J C
authors.initials: JC
authors.lastname: Lambry
authors.forename: B
authors.initials: B
authors.lastname: Bohn
authors.forename: C
authors.initials: C
authors.lastname: Poyart
authors.forename: J L
authors.initials: JL
authors.lastname: Martin
mesh_terms: D000494:Allosteric Regulation; D001665:Binding Sites; D006418:Heme / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010782:Photolysis; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman
chemical_list: D006454:Hemoglobins; D008024:Ligands; D006418:Heme; D007501:Iron