Quantifying viscosity and surface tension of multicomponent protein-nucleic acid condensates

Alshareedah, Ibraheem; Thurston, George M.; Banerjee, Priya R.

doi:10.1016/j.bpj.2021.01.005

Cited by 75 publications

(114 citation statements)

References 68 publications

Supporting

Mentioning

107

Contrasting

Order By: Relevance

“…To probe how polypeptide sequence features govern the condensate viscoelastic properties, we utilized short modular multivalent polypeptides that undergo phase separation with RNAs [41][42][43][44][45][46][47][48][49][50] . The design of these peptide sequences was inspired by naturally occurring Arginine/Glycine-rich (R/Grich) IDRs in eukaryotic ribonucleoproteins (RNPs) 51,52 , which function as promiscuous RNAbinding motifs.…”

Section: Resultsmentioning

confidence: 99%

Programmable Viscoelasticity in Protein-RNA Condensates with Disordered Sticker-Spacer Polypeptides

Alshareedah

Moosa

Banerjee

2021

Preprint

Self Cite

View full text Add to dashboard Cite

The rheological properties of biological matters play a fundamental role in many cell processes. At the organelle level, liquid-liquid phase separation of multivalent proteins and RNAs drives the formation of biomolecular condensates that facilitate dynamic compartmentalization of cellular biochemistry1. With recent advances, it is becoming increasingly clear that the structure and rheological properties of these condensates are critical to their cellular functions2,3. Meanwhile, aberrant liquid-to-solid transitions in some cellular condensates are implicated in neurodegenerative disorders4. Within the limits of two extreme material states, viz., viscous liquid and amorphous or fibrillar solid, there lies a spectrum of materials known as viscoelastic fluids. Viscoelastic fluids behave as an elastic solid at time-scales shorter than their network reconfiguration time but as a viscous fluid at longer time-scales. Viscoelasticity of biomolecular condensates may constitute an adaptive mechanism for sensing mechanical stress and regulating biochemical processes5. From an engineering standpoint, viscoelastic fluids hold great potential for designing soft biomaterials with programmable mechanosensitivity6,7. Here, employing microrheology with optical tweezers, we demonstrate how multivalent disordered sticker-spacer8,9 polypeptides undergoing associative phase separation with RNA can be designed to control the frequency-dependent viscoelastic behavior of their condensates. Utilizing linear repeat polypeptides inspired by natural RNA-binding sequences, we show that polypeptide-RNA condensates behave as Maxwell fluids, with viscoelastic behavior that can be fine-tuned by the identity of the sticker and spacer residues. The sequence heuristics that we uncovered allowed us to create biomolecular condensates spanning two orders of magnitude in their viscous and elastic responses to the applied mechanical stress. This sequence-encoded regulation of viscoelasticity in disordered polypeptide-RNA condensates establishes a link between the molecular architecture of the polypeptide chains and the rheological properties of the resulting condensates at the mesoscale, enabling a route to engineer soft biomaterials with programmable mechanics.

show abstract

Section: Resultsmentioning

confidence: 99%

Programmable Viscoelasticity in Protein-RNA Condensates with Disordered Sticker-Spacer Polypeptides

Alshareedah

Moosa

Banerjee

2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Previous studies have highlighted the challenges associated with measuring condensate surface tensions due to the small size of protein droplets 6,84 . Nonetheless, there are available estimates of this magnitude for ribonucleoprotein condensates, and these measurements demonstrate that surfactant proteins can reduce γ by orders of magnitude 22 .…”

Section: Surfactant Concentration Critically Modulates Droplet Sizementioning

confidence: 99%

Size Conservation Emerges Spontaneously in Biomolecular Condensates Formed by Scaffolds and Surfactant Clients

Sanchez-Burgos

Joseph

Collepardo-Guevara

et al. 2021

Preprint

View full text Add to dashboard Cite

Biomolecular condensates are liquid-like membraneless compartments that contribute to the spatiotemporal organization of proteins, RNA, and other biomolecules inside cells. Some membraneless compartments, such as nucleoli, are dispersed as different condensates that do not grow beyond a certain size, or do not present coalescence over time. In this work, using a minimal protein model, we show that phase separation of binary mixtures of scaffolds and low-valency clients that can act as surfactants—i.e., that significantly reduce the droplet surface tension—can yield either a single drop or multiple droplets that conserve their sizes on long timescales (herein ‘multidroplet size-conserved’), depending on the scaffold to client ratio. Our simulations demonstrate that protein connectivity and condensate surface tension regulate the balance between these two scenarios. Multidroplet size-conserved behavior spontaneously arises at increasing surfactant-to-scaffold concentrations, when the interfacial penalty for creating small liquid droplets is sufficiently reduced by the surfactant proteins that are preferentially located at the interface. In contrast, low surfactant-to-scaffold concentrations enable continuous growth and fusion of droplets without restrictions. Overall, our work proposes one potential thermodynamic mechanism to help rationalize how size-conserved coexisting condensates can persist inside cells—shedding light on the roles of general biomolecular features such as protein connectivity, binding affinity, and droplet composition in this process.

show abstract

“…Measurements of surface tension rely heavily on the fusion kinetics between two condenstates 17 . While significant improvements have been made 23,24 , the fusion assay is intrinsically limited because only a ratio of surface tension to viscosity can be estimated 12 . Therefore, a user-friendly technique that can directly measure both surface tension and viscosity of biomolecular condensates is still missing.…”

Section: Main Textmentioning

confidence: 99%

“…Many proteins tend to wet and adsorb onto solid surfaces 4,16,23,24,34 . While potentially mediating important biological processes 15,16,34 , this wetting effect can introduce significant artifacts in measurements that rely on the fusion kinetics or morphology of condensates 12,23,24 . In contrast, the contribution of R c in eq.…”

Section: Main Textmentioning

confidence: 99%

See 1 more Smart Citation

More than just oil droplets in water: surface tension and viscosity of protein condensates quantified by micropipette aspiration

Wang

Milovanović

et al. 2021

Preprint

View full text Add to dashboard Cite

The material properties of biomolecular condensates play pivotal roles in many biological and pathological processes. Despite the rapid increase in the number of biomolecules identified that undergo liquid-liquid phase separation (LLPS), quantitative studies of the resulting condensates have been severely lagging behind. Here, we develop a micropipette-based technique, which uniquely allows quantifications of both the surface tension and viscosity of biomolecular condensates, independent of labeling and surface wetting effects. We demonstrate the accuracy and versatility of this technique by measuring condensates of LAF-1 RGG domains and a polymer-based aqueous two-phase system (ATPS). We anticipate this technique will be widely applicable to biomolecular condensates and will resolve several limitations regarding current approaches.

show abstract

Quantifying viscosity and surface tension of multicomponent protein-nucleic acid condensates

Cited by 75 publications

References 68 publications

Programmable Viscoelasticity in Protein-RNA Condensates with Disordered Sticker-Spacer Polypeptides

Programmable Viscoelasticity in Protein-RNA Condensates with Disordered Sticker-Spacer Polypeptides

Size Conservation Emerges Spontaneously in Biomolecular Condensates Formed by Scaffolds and Surfactant Clients

More than just oil droplets in water: surface tension and viscosity of protein condensates quantified by micropipette aspiration

Contact Info

Product

Resources

About