title: Heme-linked ionization and ligand binding produce identical changes of proximal heme stereochemistry in reduced horseradish peroxidase. Evidence for existence of two protein conformations.
abstract: The visible and near infrared magnetic circular dichroism spectra of chemically reduced horseradish peroxidase at neutral and alkaline pH values and 5-coordinate protoheme-(2-methylimidazole) at pH 9.1 were compared at 4.2 K with those of photolysis products of their carbon monoxide complexes. From the results obtained we concluded that: (i) there are two protein conformations of HRP which determine the geometry of the Fe-N(His) bond; (ii) the transition from one conformation (heme stereochemistry) to another can be induced by either heme-linked ionization or ligand binding; (iii) a trigger mechanism for switching between two conformations has to exist.
authors.affiliation: Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow.
authors.forename: Y A
authors.initials: YA
authors.lastname: Sharonov
authors.forename: V F
authors.initials: VF
authors.lastname: Pismensky
authors.forename: E G
authors.initials: EG
authors.lastname: Yarmola
mesh_terms: D002942:Circular Dichroism; D003080:Cold Temperature; D006418:Heme / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010782:Photolysis; D011487:Protein Conformation
chemical_list: D007477:Ions; D006418:Heme; D006735:Horseradish Peroxidase; D010544:Peroxidases