Structure–Function Properties in Disordered Condensates

Abstract

Biomolecular condensates appear throughout the cell serving a wide variety of functions. Many condensates appear to form by the assembly of multivalent molecules, which produce phase-separated networks with liquidlike properties. These networks then recruit client molecules, with the total composition providing functionality. Here we use a model system of poly-SUMO and poly-SIM proteins to understand client−network interactions and find that the structure of the network plays a strong role in defining client recruitment and thus functionality. The basic unit of assembly in this system is a zipperlike filament composed of alternating poly-SUMO and poly-SIM molecules. These filaments have defects of unsatisfied bonds that allow for both the formation of a 3D network and the recruitment of clients. The filamentous structure constrains the scaffold stoichiometries and the distribution of client recruitment sites that the network can accommodate. This results in a nonmonotonic client binding response that can be tuned independently by the client valence and binding energy. These results show how the interactions within liquid states can be disordered yet still contain structural features that provide functionality to the condensate.

Motif-pattern dependence of biomolecular phase separation driven by specific interactions

“…Sequence also influences the network structure of the dense phase, where most sequences form few correlated bonds but a small subset (such as ℓ = 1 and ℓ = 12) form longer aligned segments. It has recently been shown that such aligned “zippers” can tune functional properties such as client recruitment [ 38 ], providing another link between sequence and function.…”

Multiplexed Delivery of Synthetic (Un)Conjugatable Ubiquitin and SUMO2 Enables Simultaneous Monitoring of Their Localization and Function in Live Cells

“…With Ub 5 and SUMO2 7 probes in hand, we turned our attention for simultaneous live cell delivery. We used low micromolar concentration of these probes to avoid substantial effects on the endogenous Ub and SUMO2 concentrations, which are estimated to be in ∼80‐100 micromolar range [30,31] . We mixed probes Ub 5 and SUMO2 7 with the commercial enhanced green fluorescent protein (EGFP) in PBS, containing the non‐ionic surfactant pluronic™ F‐68.…”

“…We used low micromolar concentration of these probes to avoid substantial effects on the endogenous Ub and SUMO2 concentrations, which are estimated to be in ~80-100 micromolar range. [30,31] We mixed probes Ub 5 and SUMO2 7 with the commercial enhanced green fluorescent protein (EGFP) in PBS, containing the non-ionic surfactant pluronic™ F-68. We included EGFP to test the efficacy of MBL with larger proteins and to compare its distribution to Ub and SUMO2.…”

Model biomolecular condensates have heterogeneous structure quantitatively dependent on the interaction profile of their constituent macromolecules

“…29 Empirically classifying biomolecular condensates on a spectrum from fluid (healthy) to rigid (disease) motivates us to learn how their material properties arise from their constituent IDPs. 39–41 But although an enormous amount of experimental data is accessible in online databases, 42–44 via web-based interfaces (), 45 there is no mechanistic understanding of how IDP molecular architecture controls the structure of their dense phase.…”