Structure of inhibitor-bound mammalian complex I

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Mitochondrial complex I is crucial for cellular energy production via oxidative phosphorylation.
• Previous cryo-electron microscopy (cryo-EM) studies provided near-complete models of mammalian complex I.
• The precise mechanisms of long-range energy coupling within complex I remain under investigation.

Purpose of the Study:

• To elucidate the molecular principles of energy transduction in mammalian complex I.
• To determine the binding mode of inhibitors in the ubiquinone-binding site of complex I.
• To understand the mechanisms of inhibition and substrate reduction in complex I.

Main Methods:

• 3.0-Å resolution cryo-electron microscopy (cryo-EM) structure determination of mouse heart mitochondrial complex I.
• Co-crystallization with a substrate-like inhibitor, piericidin A.
• Functional assays and computational studies to analyze inhibitor binding and substrate reduction.

Main Results:

• The cryo-EM structure reveals piericidin A bound in the ubiquinone-binding active site of complex I.
• Evidence suggests two piericidin A molecules bind end-to-end within the substrate binding channel.
• Competitive inhibitor binding poses and their implications for substrate reduction were demonstrated.

Conclusions:

• The study provides detailed structural insights into inhibitor binding within mammalian complex I.
• Findings contribute to understanding the mechanisms of energy transduction and substrate reduction.
• The research clarifies aspects of complex I function relevant to oxidative phosphorylation.