Figure 3.

The linkers (in brown) in Cullin-RING E3 ligases (CRL) allosterically regulate the ubiquitination. CRL consists four components, RING-box protein (RBX, cyan), cullin (yellow), adaptor (orange), and substrate-binding protein (SBP, blue). RBX binds to E2 (green) and SBP binds to substrate protein (S, pink). Ubiquitin (Ub) is transferred from E2 to target protein. CRL works as a flexible two arm machine. RBX and SBP are the two flexible arms, and the cullin serves as the flexible scaffold. They work together to adjust the E2-ubiquitin distance for the efficient ubiquitination.