Peroxynitrite-mediated oxidative modifications of myosin and implications on structure and function

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Myosin is a crucial motor protein involved in muscle contraction.
• Oxidative stress, particularly from peroxynitrite, can lead to protein damage and functional impairment.
• Understanding the specific molecular mechanisms of peroxynitrite-induced myosin dysfunction is important for cellular health.

Purpose of the Study:

• To investigate the molecular mechanisms underlying peroxynitrite-induced functional impairment of myosin.
• To determine how different reaction conditions affect peroxynitrite's interaction with myosin.
• To identify the key post-translational modifications responsible for myosin dysfunction.

Main Methods:

• Studying myosin's MgATPase activity under various peroxynitrite reaction conditions.
• Assessing basal and actin-stimulated ATPase activities.
• Quantifying protein carbonylation and tyrosine nitration.
• Evaluating the role of sulphydryl oxidation and its reversibility.

Main Results:

• Peroxynitrite enhanced basal MgATPase activity (up to 2-fold) while inhibiting actin-stimulated ATPase activity.
• Functional alterations were dependent on the reaction medium.
• Changes in ATPase activity correlated with increased protein carbonyl formation in myosin.
• Inhibition was more potent when tyrosine nitration and sulphydryl reactivity were lower.
• Reverting sulphydryl oxidation did not restore myosin function.

Conclusions:

• Protein carbonylation is a critical post-translational modification in peroxynitrite-induced myosin functional impairment.
• The extent of myosin dysfunction is influenced by reaction conditions affecting peroxynitrite chemistry.
• Tyrosine nitration and sulphydryl oxidation are less critical than carbonylation in this context.