Predicting Rubisco:Linker Condensation from Titration in the Dilute Phase

TL;DR

This paper develops a semi-analytical model to predict Rubisco condensation behavior in algae, fitting experimental data to estimate molecular properties and compare with microscopy observations.

Contribution

It introduces a semi-analytical approach for modeling Rubisco-linker aggregation and validates predictions with experimental data.

Findings

Model accurately predicts titration curves from experimental data.

Estimated concentrations for condensation match microscopy observations.

Provides a quantitative framework for understanding Rubisco condensation.

Abstract

The condensation of Rubisco holoenzymes and linker proteins into 'pyrenoids', a crucial super-charger of photosynthesis in algae, is qualitatively understood in terms of 'sticker-and-spacer' theory. We derive semi-analytical partition sums for small Rubisco:linker aggregates, which enable the calculation of both dilute-phase titration curves and dimerisation diagrams. By fitting the titration curves to Surface Plasmon Resonance and Single-Molecule Fluorescence Microscopy data, we extract the molecular properties needed to predict dimerisation diagrams. We use these to estimate typical concentrations for condensation, and successfully compare these to microscopy observations.