Predicting Rubisco-Linker Condensation from Titration in the Dilute Phase

Area of Science:

• Biophysics
• Photosynthesis research
• Molecular biology

Background:

• Pyrenoids are vital organelles in algae, enhancing photosynthetic efficiency by concentrating Rubisco.
• The "sticker-and-spacer" theory qualitatively describes the condensation of Rubisco holoenzymes and linker proteins into pyrenoids.
• Quantitative understanding of pyrenoid formation requires detailed molecular properties.

Purpose of the Study:

• To develop a quantitative model for Rubisco-linker aggregate formation.
• To predict the conditions necessary for pyrenoid condensation.
• To determine molecular properties governing pyrenoid assembly.

Main Methods:

• Derivation of semianalytical partition sums for Rubisco-linker aggregates.
• Calculation of dilute-phase titration curves and dimerization diagrams.
• Fitting model predictions to experimental data from surface plasmon resonance and single-molecule fluorescence microscopy.

Main Results:

• Successfully derived partition sums to model Rubisco-linker condensation.
• Extracted key molecular properties by fitting titration curves to experimental data.
• Estimated typical concentrations for pyrenoid condensation, validated by microscopy.

Conclusions:

• The quantitative model accurately predicts pyrenoid condensation concentrations based on molecular properties.
• This work provides a framework for understanding the biophysics of organelle formation in photosynthesis.
• Findings advance the study of Rubisco concentration mechanisms and photosynthetic efficiency in algae.