Phase-separating pyrenoid proteins form complexes in the dilute phase

Guanhua He, Trevor GrandPre, Hugh Wilson, Yaojun Zhang, Martin C. Jonikas, Ned S. Wingreen, Quan Wang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


While most studies of biomolecular phase separation have focused on the condensed phase, relatively little is known about the dilute phase. Theory suggests that stable complexes form in the dilute phase of two-component phase-separating systems, impacting phase separation; however, these complexes have not been interrogated experimentally. We show that such complexes indeed exist, using an in vitro reconstitution system of a phase-separated organelle, the algal pyrenoid, consisting of purified proteins Rubisco and EPYC1. Applying fluorescence correlation spectroscopy (FCS) to measure diffusion coefficients, we found that complexes form in the dilute phase with or without condensates present. The majority of these complexes contain exactly one Rubisco molecule. Additionally, we developed a simple analytical model which recapitulates experimental findings and provides molecular insights into the dilute phase organization. Thus, our results demonstrate the existence of protein complexes in the dilute phase, which could play important roles in the stability, dynamics, and regulation of condensates.

Original languageEnglish (US)
Article number19
JournalCommunications Biology
Issue number1
StatePublished - Dec 2023

All Science Journal Classification (ASJC) codes

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences
  • Medicine (miscellaneous)


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