Phase-separating pyrenoid proteins form complexes in the dilute phase.

TitlePhase-separating pyrenoid proteins form complexes in the dilute phase.
Publication TypeJournal Article
Year of Publication2023
AuthorsHe, G, GrandPre, T, Wilson, H, Zhang, Y, Jonikas, MC, Wingreen, NS, Wang, Q
JournalCommun Biol
Volume6
Issue1
Pagination19
Date Published2023 Jan 07
ISSN2399-3642
KeywordsPlastids, Ribulose-Bisphosphate Carboxylase
Abstract

<p>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.</p>

DOI10.1038/s42003-022-04373-x
Alternate JournalCommun Biol
PubMed ID36611062
PubMed Central IDPMC9825591