Our cells have a fleet of 300 molecular machines, called cullin-RING ligases, or „CRLs“ for short, that each is capable of triggering destruction of specific proteins for the well-being of our cells. However, most proteins are needed, therefore only those that block newly required cellular paths or that are toxic should be destroyed. The destructive potential of CRLs is tightly controlled. CRLs are switched on only temporarily, when needed. Researchers at MPI of Biochemistry and University of Waterloo have developed a new way to detect those CRLs in the fleet that are „on”, which reveals the CRLs deployed to solve cellular stresses and to perform the actions of some anti-cancer drugs.