Cryo-EM structure and function of S. pombe complex IV with bound respiratory supercomplex factor.

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Respiration

Background:

• Fission yeast (Schizosaccharomyces pombe) is a key model organism for eukaryotic studies.
• Respiratory Complex IV (CIV) is crucial for cellular respiration and energy production.
• Understanding CIV structure and function provides insights into mitochondrial diseases.

Purpose of the Study:

• To investigate the structure and function of respiratory complex IV (CIV) from S. pombe.
• To elucidate the role of associated proteins in CIV activity.
• To compare S. pombe CIV with its mammalian counterparts.

Main Methods:

• Cryo-electron microscopy (cryo-EM) for structural determination.
• Spectroscopy to analyze enzyme kinetics and reaction mechanisms.
• Affinity purification to isolate intact respiratory complex IV.
• AlphaFold-Multimer modeling for protein-protein interactions.

Main Results:

• The reaction kinetics of reduced S. pombe CIV with oxygen occur on a microsecond to millisecond timescale, mirroring mammalian CIV.
• Cryo-EM revealed a eleven-subunit CIV structure with a bound hypoxia-induced gene 1 (Hig1) domain of respiratory supercomplex factor 2 (Rcf2).
• Rcf2 binds to CIV independently of a CIII-CIV supercomplex, indicating it's a CIV component. AlphaFold-Multimer suggests mutually exclusive binding of Rcf1 and Rcf2 Hig1 domains.

Conclusions:

• Rcf2 is an integral component of fission yeast respiratory complex IV.
• The binding of Rcf2 to CIV is independent of supercomplex formation.
• Differential functional effects of Rcf1 and Rcf2 likely stem from their non-Hig1 domain interactions with CIV.