Evidence for widespread cytoplasmic structuring into mesoscopic condensates

Eukaryotic cytoplasm organizes itself via membrane-bound organelles and membrane-less biomolecular condensates (BMCs). Known BMCs exhibit liquid-like properties and are typically visualized on the scale of ~1 µm. They have been studied mostly by microscopy, examining select individual proteins. Here, we investigate the global organization of native cytoplasm with quantitative proteomics, using differential pressure filtration and dilution experiments. These assays revealed that BMCs form predominantly at the mesoscale of ~100 nm, which we validated via microscopy. Our data indicate that at least 18% of the proteome is organized via such mesoscale BMCs, suggesting that cells widely employ dynamic liquid-like clustering to organize their cytoplasm, at surprisingly small length scales.