Predicting Rubisco-Linker Condensation from Titration in the Dilute Phase
Published in Physical Review Letters, 2024
Abstract
The condensation of Rubisco holoenzymes and linker proteins into “pyrenoids,” a crucial supercharger of photosynthesis in algae, is qualitatively understood in terms of “sticker-and-spacer” theory. We derive semianalytical partition sums for small Rubisco-linker aggregates, which enable the calculation of both dilute-phase titration curves and dimerization diagrams. By fitting the titration curves to surface plasmon resonance and single-molecule fluorescence microscopy data, we extract the molecular properties needed to predict dimerization diagrams. We use these to estimate typical concentrations for condensation, and successfully compare these to microscopy observations.
Description
In this contribution, the York Physics of Pyrenoids Project (YP3) consortium joined forces to parametrise and experimentally validate a model for Rubisco dimerisation, and by proxy liquid-liquid phase separation. Using affinity measurements of variants of EPYC1 with different numbers of stickers for Rubisco using single molecular dilute binding assays (SMDBAs), based on Slimfield microscopy, as well as Surface Plasmon Resonance measurements a binding energy between EPYC1 and Rubisco could be described. By extending this binding energy for use in a statistical physics approach developed by Charley Schaefer to predict dimerization concentrations, a critical concentration for liquid-liquid phase separation (LLPS) could be predicted. Strikingly, the predicted values and observed concentrations compare execptionally well.
Cite: Payne-Dwyer, A. et al. (2024). "Predicting Rubisco-Linker Condensation from Titration in the Dilute Phase". Physical review letters, 132 (21), p.218401. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.218401