S-nitrosation of mitochondrial complex I depends on its structural conformation

Area of Science:

• Biochemistry
• Cellular Respiration
• Mitochondrial Function

Background:

• Nitric oxide (NO) is known to inhibit mitochondrial respiration via S-nitrosation of NADH: ubiquinone oxidoreductase (complex I).
• The physiological relevance and cellular mechanisms of NO-induced complex I nitrosation remain unclear.
• The conformational state of complex I influences its susceptibility to modification and inhibition.

Purpose of the Study:

• To investigate the role of mitochondrial complex I conformational states in its regulation by nitric oxide-related species.
• To determine the cellular mechanisms underlying the interaction between complex I and nitrosating agents under physiological conditions.

Main Methods:

• Enzymatic assays were used to assess the activity of different conformational states of mitochondrial complex I.
• The susceptibility of active and deactivated complex I to inhibition by nitrosothiols and peroxynitrite was evaluated.
• The direct effect of nitric oxide on both conformational states of complex I was examined.

Main Results:

• Only the deactivated, idle form of mitochondrial complex I was inhibited by nitrosothiols and peroxynitrite.
• The active form of complex I demonstrated resistance to inhibition by these nitrosating agents.
• Neither the active nor the deactivated form of complex I was directly inhibited by nitric oxide itself.

Conclusions:

• The active/deactive transition of mitochondrial complex I is a critical regulatory mechanism for its interaction with nitric oxide-related species.
• This conformational regulation influences cellular respiration and may have implications for hypoxic or pathophysiological conditions.
• Understanding this mechanism provides insights into cellular responses to oxidative stress and altered oxygen availability.