Energetic robustness to large scale structural fluctuations in a photosynthetic supercomplex

Area of Science:

• Photosynthesis research
• Structural biology
• Biophysics

Background:

• Photosynthetic organisms utilize large protein supercomplexes to efficiently convert solar energy.
• Precise chlorophyll positioning within these complexes is crucial for rapid energy transfer.
• The impact of structural variability on energy transfer efficiency remained unclear.

Purpose of the Study:

• To investigate structural heterogeneity in the cyanobacterial PSI-IsiA photosynthetic supercomplex.
• To understand how energy transfer efficiency is maintained despite observed structural variations.

Main Methods:

• Cryo-electron microscopy (Cryo-EM) was used to observe the 2-MDa PSI-IsiA supercomplex.
• Single-molecule measurements were employed to assess energy transfer dynamics.
• Structure-based calculations were performed to analyze energy transfer mechanisms.

Main Results:

• Cryo-EM revealed significant structural heterogeneity in the PSI-IsiA supercomplex, with large variances in IsiA positioning relative to PSI.
• Single-molecule measurements demonstrated efficient IsiA-to-PSI energy transfer across all observed conformations.
• Calculations indicated that energy transfer is consistently maintained and can increase in specific conformations.

Conclusions:

• The study elucidates a mechanism for robust energy transfer in photosynthetic supercomplexes.
• Antennae design appears to mitigate structural fluctuations in flexible membranes.
• This provides insight into how photosynthetic efficiency is maintained despite dynamic structural variations.