Predicting Rubisco:Linker Condensation from Titration in the Dilute Phase

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.
Comment: v2: correction in the single-Rubisco calculations; v3: added single-Rubisco experimental work; v4: model and experiments extended to describe Rubisco condensation