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Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
Published on: June 16, 2023
Architecture and assembly dynamics of the essential mitochondrial chaperone complex TIM9·10·12
Katharina Weinhäupl1, Yong Wang2, Audrey Hessel1
1Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), 71, Avenue Des Martyrs, 38044 Grenoble, France.
Mitochondrial Tim chaperones, TIM9·10 and TIM9·10·12, dynamically exchange subunits. This dynamic equilibrium, with a 2:3:1 Tim9:Tim10:Tim12 stoichiometry, allows mitochondria to regulate inter-membrane space chaperone levels.
Area of Science:
- Mitochondrial protein transport
- Molecular chaperones
- Structural biology
Background:
- Tim chaperones are essential for transporting proteins across mitochondrial membranes.
- The TIM9·10·12 complex is crucial for anchoring client proteins to the inner-membrane insertase TIM22.
- The exact subunit composition and dynamics of the TIM9·10·12 complex were previously debated.
Purpose of the Study:
- To determine the structural model and subunit stoichiometry of the TIM9·10·12 complex.
- To investigate the dynamic behavior of TIM9·10 and TIM9·10·12 hexamers and their subunits.
- To understand the role of conformational dynamics in mitochondrial chaperone function.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy
- Small-angle X-ray scattering (SAXS)
- Molecular Dynamics (MD) simulations
Main Results:
- A structural model for the TIM9·10·12 assembly with a 2:3:1 stoichiometry (Tim9:Tim10:Tim12) was derived.
- Both TIM9·10 and TIM9·10·12 hexamers exist in a dynamic equilibrium with their subunits, with exchange occurring on a minutes timescale.
- Subunits exhibit significant conformational dynamics, with alpha-helices stabilizing upon hexamer formation.
Conclusions:
- The study provides a high-resolution structural model for the TIM9·10·12 complex.
- Continuous subunit exchange is proposed as a mechanism for mitochondria to control inter-membrane space chaperone levels.
- Conformational flexibility of Tim subunits is critical for chaperone function and assembly.
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