Role of K⁺ binding residues in stabilization of heme spin state of Leishmania major peroxidase

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• 作者：Swati Pal¹ ; Rajesh K. Yadav¹ ; Subrata Adak ; ^{adaks@iicb.res.in}
• 关键词：APX ; plant ascorbate peroxidase ; LmP ; Leishmania major peroxidase ; CCP ; yeast cytochrome c peroxidase ; HS ; high spin ; LS ; low spin ; WT ; wild type
• 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
• 出版年：2012
• 期刊代码：161_15709639
• 类别：bio
• 出版时间：August, 2012
• 卷：1824
• 期：8
• 页码：1002-1007
• 文件大小：447 K

摘要

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 掳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 H₂O₂. 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.