Peroxidase activity of cytochrome c in its compact state depends on dynamics of the heme region |
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Institution: | 1. Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04154 Košice, Slovakia;2. Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia;3. Centre for Interdisciplinary Biosciences, P. J. Šafárik University in Košice, Jesenná 5, 04154 Košice, Slovakia;1. Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan;2. Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan;3. PRESTO, Japan Science and Technology Agency, Sapporo 060-0810, Japan;1. Research Institute of Applied Sciences, ACECR, Shahid Beheshti University, Tehran, Iran;2. Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran;3. Department of Life Science Engineering, Faculty of New Sciences & Technologies, University of Tehran, Tehran, Iran;4. Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran |
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Abstract: | Cytochrome c (cyt c) is a small globular hemoprotein with the main function as an electron carrier in mitochondrial respiratory chain. Cyt c possesses also peroxidase-like activity in the native state despite its six-coordinated heme iron. In this work, we studied the effect of increasing urea concentration in the range from 0 M to 6 M at pH 7 (pH value of the bulk solvent) and pH 5 (pH value close to negatively charged membrane) on peroxidase-like activity of cyt c. We show that peroxidase-like activity, measured by guaiacol oxidation and the ferrous oxidation in xylenol orange methods, correlates with the accessibility of the heme iron, which was assessed from the association rate constant of cyanide binding to cyt c. Cyt c peroxidase-like activity linearly increases in the pre-denaturational urea concentrations (0–4 M) at both studied pHs without an apparent formation of penta-coordinated state of the heme iron. Our results suggest that dynamic equilibrium among the denaturant-induced non-native coordination states of cyt c, very likely due to reversible unfolding of the least stable foldons, is pre-requisite for enhanced peroxidase-like activity of cyt c in its compact state. Dynamic replacement of the native sixth coordination bond of methionine-80 by lysines (72, 73, and 79) and partially also by histidines (26 and 33) provides an efficient way how to increase peroxidase-like activity of cyt c without significant conformational change at physiological conditions. |
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