Atomic structures of respiratory complex III₂, complex IV, and supercomplex III₂-IV from vascular plants

Area of Science:

• Biochemistry
• Structural Biology
• Plant Science

Background:

• Mitochondrial respiration is crucial for energy production in plants.
• Complex III (CIII₂) and Complex IV (CIV) form supercomplexes (SC III₂+IV) vital for respiration.
• The structures of these plant mitochondrial complexes were previously unknown.

Purpose of the Study:

• To determine the atomic structures of plant mitochondrial CIII₂, CIV, and SC III₂+IV.
• To identify plant-specific structural features and subunit compositions.
• To investigate the dynamics and functional mechanisms of these complexes.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) was used to determine the structures.
• Analysis of conformational heterogeneity was performed on CIII₂.
• Comparative structural analysis with yeast and bacterial complexes.

Main Results:

• Atomic models of Vigna radiata CIII₂, CIV, and SC III₂+IV were obtained.
• Plant-specific differences in the CIII₂ MPP domain and CIV subunit composition were identified.
• Long-range movements in CIII₂ and a non-H channel proton translocation mechanism in CIV were suggested.
• The SC III₂+IV interface shows significant divergence from non-plant homologs.

Conclusions:

• The determined structures challenge existing assumptions about plant mitochondrial respiratory complexes.
• New mechanistic hypotheses for plant respiration and supercomplex formation are proposed.
• Structural insights advance our understanding of plant energy metabolism.