title: Role of K(+) binding residues in stabilization of heme spin state of Leishmania major peroxidase.
abstract: The endogenous cation in peroxidases may contribute to the type of heme coordination. Here a series of ferric and ferrous derivatives of wild-type Leishmania major peroxidase (LmP) and of engineered K(+) site mutants of LmP, lacking potassium cation binding site, has been examined by electronic absorption spectroscopy at 25°C. Using UV-visible spectrophotometry, we show that the removal of K(+) binding site causes substantial changes in spin states of both the ferric and ferrous forms. The spectral changes are interpreted to be, most likely, due to the formation of a bis-histidine coordination structure in both the ferric and ferrous oxidation states at neutral pH 7.0. Stopped flow spectrophotometric techniques revealed that characteristics of Compound I were not observed in the K(+) site double mutants in the presence of H(2)O(2). Similarly electron donor oxidation rate was two orders less for the K(+) site double mutants compared to the wild type. These data show that K(+) functions in preserving the protein structure in the heme surroundings as well as the spin state of the heme iron, in favor of the enzymatically active form of LmP.
authors.affiliation: CSIR-Indian Institute of Chemical Biology, Kolkata, India.
authors.forename: Swati
authors.initials: S
authors.lastname: Pal
authors.forename: Rajesh K
authors.initials: RK
authors.lastname: Yadav
authors.forename: Subrata
authors.initials: S
authors.lastname: Adak
mesh_terms: D001665:Binding Sites; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D007891:Leishmania / Q000201:enzymology*; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000737:chemistry* / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D006418:Heme; D006861:Hydrogen Peroxide; D007501:Iron; D009195:Peroxidase; D011188:Potassium