title: Role of the arginine-45 salt bridge in ligand dissociation from sperm whale carboxymyoglobin as probed by photoacoustic calorimetry.
abstract: The dynamics of the enthalpy and volume changes found in the photodissociation of CO from sperm whale carboxymyoglobin and two site-directed mutants in which arginine-45 is replaced by glycine and asparagine are examined by photoacoustic calorimetry. An intermediate is observed whose lifetime at 20 degrees C is 700 ns. The enthalpy of the intermediate increases by approximately 7 kcal/mol upon replacing arginine-45 with either asparagine or glycine. These observations support recent proposals that an arginine-45 salt bridge is broken upon ligand dissociation.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
authors.forename: J A
authors.initials: JA
authors.lastname: Westrick
authors.forename: K S
authors.initials: KS
authors.lastname: Peters
authors.forename: J D
authors.initials: JD
authors.lastname: Ropp
authors.forename: S G
authors.initials: SG
authors.lastname: Sligar
mesh_terms: D000162:Acoustics; D000818:Animals; D001120:Arginine; D001483:Base Sequence; D002151:Calorimetry / Q000379:methods*; D002248:Carbon Monoxide / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004058:Diffusion; D008969:Molecular Sequence Data; D009154:Mutation; D009211:Myoglobin / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis; D010777:Photochemistry; D015202:Protein Engineering; D011522:Protons; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014907:Whales
chemical_list: D009211:Myoglobin; D009838:Oligodeoxyribonucleotides; D011522:Protons; D011993:Recombinant Fusion Proteins; C018013:carboxymyoglobin; D002248:Carbon Monoxide; D001120:Arginine