Ubiquitin chains, liquid droplets, and the gathering of proteasomes under stress Every cell is constantly making proteins and constantly getting rid of them. Some proteins are damaged, some are misfolded, some were made in excess, and some have simply finished their jobs. To dispose of them, the cell marks each one with a small protein called ubiquitin, 76 amino acids long. One ubiquitin is often attached to another, and another to that, building a chain. The chain is a label