Structural insights into G domain dimerization and pathogenic mutation of OPA1

Area of Science:

• Mitochondrial biology
• Molecular cell biology
• Neuroscience

Background:

• Inner mitochondrial membrane fusion is essential for cellular function and is regulated by the dynamin-like GTPase OPA1.
• Mutations in the human OPA1 gene lead to optic atrophy, a neurodegenerative disease, but the underlying molecular mechanisms remain unclear.

Purpose of the Study:

• To elucidate the molecular basis of OPA1-mediated membrane fusion and its role in optic atrophy pathogenesis.
• To determine the crystal structure of the minimal GTPase domain (MGD) of human OPA1.

Main Methods:

• X-ray crystallography to determine the structure of OPA1-MGD.
• Biochemical assays to investigate nucleotide-dependent and independent dimerization.
• Analysis of OPA1 mutations in relation to mitochondrial morphology.

Main Results:

• The crystal structure of OPA1-MGD revealed unique features in its catalytic core compared to other dynamin-like proteins.
• OPA1-MGD forms nucleotide-dependent dimers crucial for mitochondrial morphology and membrane-stimulated GTP hydrolysis.
• An N-terminal extension mediates nucleotide-independent dimerization, facilitating efficient membrane association.

Conclusions:

• OPA1 exhibits a multifaceted assembly mechanism involving both nucleotide-dependent and independent dimerization.
• These structural and functional insights explain the pathogenic effects of most OPA1 mutations in optic atrophy.