Boron stabilizes peroxide mediated changes in the structure of heme proteins

Boron is reported in this study to stabilize the structure of heme proteins exposed to peroxides. The oxidized heme protein (15 μM) was treated with H2O2 (10 mM) in 1 M glycine–NaOH buffer (pH 9.2) at 25 °C in absence/presence of boron, and characterized by visible absorption spectroscopy, gel exclusion chromatography, native PAGE, HPLC and DLS. Spectral analysis of exposed heme proteins revealed a decrease in absorbance in the Soret region, which was stabilized by boron. The native PAGE analysis of exposed heme proteins showed high molecular weight products; the band intensity was lesser in presence of boron. Further, elution profile of the exposed heme proteins on Sephadex G-200 column and HPLC revealed more than one peak (aggregate formation) when compared to the respective untreated proteins. DLS, which measures the hydrodynamic radius (RH), was used to ascertain whether the peaks correspond to monomer, dimer or aggregate forms. The RH of boron pretreated heme proteins was close to RH of the respective heme protein. Non-heme protein RNase did not show any change when exposed to peroxide. Taken together, results conclude that boron stabilizes the structure of heme proteins, which might be due to specific sites on heme proteins that can bind to borate ions.