Membrane wetting by biomolecular condensates is facilitated by mobile tethers

Biomolecular condensates frequently rely on membrane interactions for localization, recruitment, and chemical substrates. These interactions are often mediated by membrane-anchored mobile tethers, a feature overlooked by traditional wetting models. Here, we propose a general theoretical framework to study how mobile tethers impact both equilibrium and dynamic properties of condensate wetting. We show that a favorable tether-condensate interaction leads to tether enrichment at the condensate-membrane interface, which reduces the surface tension with the membrane and modifies the equilibrium contact angle. Increasing tether abundance on the membrane can drive transitions between wetting regimes, with only a modest binding energy required for biologically relevant scenarios. Furthermore, by helping condensates coat membranes, mobile tethers can facilitate condensate localization to junctions of membrane structures, such as the reticulated membranes inside the algal pyrenoid. These results provide a framework to study the implications of tether-mediated condensate-membrane interactions for cellular organization and function.