Cytosolissa

Cytosolissa is a proposed membrane-free cytosolic compartment described in speculative biology as a dynamic biomolecular condensate that forms within the cell cytoplasm. The concept envisions Cytosolissa arising by phase separation of multivalent proteins and RNA, creating a distinct, though fluid, microenvironment that concentrates selected enzymes and substrates.

The condensate is not bounded by a membrane; rather, it appears as a gel-like droplet that can fuse with other condensates and exchange material with the surrounding cytosol.

Structural features are hypothetical but typically include scaffold proteins with low-complexity domains that drive assembly, along with RNA molecules that modulate viscosity and selectivity. The interior is expected to be enriched in glycolytic enzymes, nucleotide-synthesis catalysts, and lipid metabolism factors, with diffuse channels allowing substrate flux.

Proposed functions include metabolic channeling—localizing sequential reactions to accelerate throughput—and regulation of enzyme activity by microenvironmental factors such as pH, crowding, and ion concentration. Cytosolissa may also serve as a storage or sequestration site for enzymes during stress, releasing them when needs rise.

While the concept remains speculative, it provides a framework to explore how cells might organize metabolism without membranes and how synthetic biology could harness phase separation to engineer intracellular compartments.

References and experimental validation remain limited, and Cytosolissa is not part of established cell biology.