title: Versatility of the electronic structure of compound I in catalase-peroxidases.
abstract: Catalase-peroxidases (KatGs) are bifunctional heme proteins, belonging to the family of class I peroxidases, that are able to catalyze both catalatic and peroxidatic reactions within a peroxidase-like structure. We investigated the electronic structure of reaction intermediates of the catalytic cycle of KatGs by means of density functional theory (DFT) QM/MM calculations. The outcome was that the ionization state of the KatG-specific covalent adduct (Met264-Tyr238-Trp111) affects the radical character of compound I (Cpd I). Specifically, in the optimized structures, substantial radical character is observed on the proximal Trp330 when Tyr238 is protonated, whereas when Tyr238 is deprotonated the radical localizes on the Met+-Tyr(O-)-Trp adduct. These findings are not affected by protein thermal fluctuations, although details of the spin density distribution are affected by the geometry of the active site. Calculations provide structures in good agreement with the crystal structure of BpKatG Cpd I. They also provide an explanation for the experimental findings of the mobile and catalatic-specific residue Arg426 being 100% in conformation R in the X-ray structure of BpKatG treated with organic peroxides. The role of different Cpd I forms in the catalase and peroxidase reaction pathways is discussed.
authors.affiliation: Centre de Recerca en Química Teorica, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona, Spain.
authors.forename: Pietro
authors.initials: P
authors.lastname: Vidossich
authors.forename: Mercedes
authors.initials: M
authors.lastname: Alfonso-Prieto
authors.forename: Xavi
authors.initials: X
authors.lastname: Carpena
authors.forename: Peter C
authors.initials: PC
authors.lastname: Loewen
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fita
authors.forename: Carme
authors.initials: C
authors.lastname: Rovira
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D016957:Burkholderia pseudomallei / Q000201:enzymology*; D004583:Electrons; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D010544:Peroxidases / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011789:Quantum Theory
chemical_list: D001426:Bacterial Proteins; D007501:Iron; D010544:Peroxidases; C081610:catalase-peroxidase, bacteria