Pressure-Sensitive and Osmolyte-Modulated Liquid–Liquid Phase Separation of Eye-Lens γ-Crystallins

Biomolecular condensates can be functional (e.g., as membrane-less organelles) or dysfunctional (e.g., as precursors to pathological protein aggregates). A major physical underpinning of biomolecular condensates is liquid–liquid phase separation (LLPS) of proteins and nucleic acids. Here we investigate the effects of temperature and pressure on the LLPS of the eye-lens protein γ-crystallin using UV/vis and IR absorption, fluorescence spectroscopy, and light microscopy to characterize the mesoscopic phase states. Quite unexpectedly, the LLPS of γ-crystallin is much more sensitive to pressure than folded states of globular proteins. At low temperatures, the phase-separated droplets of γ-crystallin dissolve into a homogeneous solution at as low as ∼0.1 kbar whereas proteins typically unfold above ∼3 kbar. This observation suggests, in general, that organisms thriving under high-pressure conditions in the deep sea, with pressure of up to 1 kbar, have to cope with this pressure sensitivity of biomolecular cond...