Coordination of cytochrome bc₁ complex assembly at MICOS

Area of Science:

• Mitochondrial biology
• Cellular respiration
• Protein biogenesis

Background:

• Mitochondrial inner membrane proteins navigate diffusion barriers at crista junctions.
• The mitochondrial contact site and cristae organizing system (MICOS) stabilizes crista junctions.
• Nuclear-encoded proteins require import machinery to reach their inner mitochondrial membrane destinations.

Purpose of the Study:

• To investigate the role of MICOS in respiratory chain complex biogenesis.
• To identify factors mediating the connection between respiratory chain assembly intermediates and MICOS.
• To elucidate the mechanism by which respiratory complexes reach their functional sites at crista junctions.

Main Methods:

• Investigated protein-protein interactions between respiratory chain components and MICOS.
• Identified the inner membrane protein Mar26 (Fmp10) as a key player in cytochrome bc1 complex (complex III) biogenesis.
• Analyzed the role of Mar26 in coupling assembly intermediates to MICOS at crista junctions.

Main Results:

• Respiratory chain complexes and assembly intermediates are physically linked to MICOS.
• Mar26 directly couples a Rieske Fe/S protein-containing assembly intermediate to MICOS.
• Mar26 maintains an assembly-competent pool of the Rip1 protein at crista junctions, facilitating complex III maturation.

Conclusions:

• MICOS, through interaction with assembly factors like Mar26, plays a crucial role in respiratory chain biogenesis.
• The Mar26-MICOS interaction ensures efficient assembly of complex III at crista junctions.
• MICOS facilitates the spatial and temporal coordination of respiratory chain assembly by recruiting intermediates to crista junctions.