To reversibly sequester and launch chosen freight proteins, scientists engineer cells to produce a scaffold protein that forms condensates, or membraneless organelles, in the cell cytoplasm (panel 1). They then choose a particular cellular protein as freight (yellow) and genetically engineer it to be connected with a peptide tag (orange) that engages with the scaffold protein. In one variation of the method, checked in yeast cells, the researchers crafted the tag to be connected to the cargo via a photocleavable protein (blue).
