Cells in the human body must adapt their protein balance to certain situations, such as the availability of iron or an infection. These adaptations occur through a complex process in which proteins that are no longer needed or that are toxic are tagged for destruction by attaching a small protein called ubiquitin to them. This marking of a protein for destruction by tagging with ubiquitin is carried out by Cullin-RING Ligases, or “CRLs” for short. Therefore, CRLs can be considered as “destroyers” of specific protein molecules.
Overall, the CRLs are the largest collection of ubiquitin tagging machines, with more than 300 members. Researcher Lukas Henneberg explains, “You can imagine that the 300 different CRLs inside a cell are like a fleet of destroyers, each of which would be able to lock onto a different target. If a cell is exposed to an increase in iron or to infectious bacteria, the proteins that would further increase iron to toxic levels or that would prevent the immune response