Résumé
Biomolecular condensates
modulate various ion-dependent
cellular
processes and can regulate subcellular ion distributions by selective
uptake of ions. To understand these processes, it is essential to
uncover the molecular grammar governing condensate-ion interactions.
Here, we use nuclear magnetic resonance (NMR) spectroscopy of ions
and model condensate components to quantify and spatially resolve
selective ion binding to condensates and show that these interactions
follow the “law of matching water affinities”, resulting
in strong binding between proteins and chaotropic anions and between
nucleic acids and kosmotropic cations. Ion uptake into condensates
directly follows binding affinities, resulting in selective uptake
of strong-binding ions but exclusion of weak-binding ions. Ion binding
further shapes the condensate microenvironment by altering the composition,
viscosity, and interface potential. Such changes can have profound
effects on biochemical processes taking place inside condensates,
as we show for RNA duplex formation. Our findings provide a new perspective
on the role of condensate-ion interactions in cellular bio- and electrochemistry
and may aid the design of condensate-targeting therapeutics.