Peroxynitrite-Mediated Structural Changes in Histone H2A: Biochemical and Biophysical Analysis

Background: Peroxynitrite, a nitrating and oxidizing agent, is formed by the interaction between nitric oxide and superoxide radicals. H2A histone is a basic nucleoprotein and is one of the major core histones responsible for packaging DNA. It has been shown that they are highly sensitive to oxidizing and nitrating agents. Objective: Nitration of tyrosine residues in proteins by peroxynitrite is regarded as a marker of nitrosative damage. The dityrosine bond, an oxidative covalent cross-link between two tyrosines in protein, is increasingly identified as a marker of oxidative stress, aging and neurodegerative diseases. Methods: Peroxinitrite-mediated nitration and dinitration in H2A histone was assessed by various biophysical techniques. Results: The data presented in this study showed that the dityrosine content was found to be elevated in H2A histone modified with peroxynitrite. The formation of dityrosine showed a decrease in fluorescence intensity, generation of a new peak in FT-IR, increase in hydrodynamic size, and loss of secondary and tertiary structure of H2A resulting in a partially folded structure. Conclusion: We report that H2A may undergo conformational and structural changes under nitrosative and oxidative stress from the deleterious effects of peroxynitrite.