Regulation of Receptors and Transporters by Ubiquitination: New Insights into Surprisingly Similar Mechanisms

Types of ubiquitin conjugation. Gly⁷⁶ of ubiquitin is covalently attached to the ε-amino group of lysines in the substrate. Substrates can be modified with a single ubiquitin molecule at a single (monoubiquitination) or multiple (multi-monoubiquitination) lysine residues. Further ubiquitin conjugation to the lysine residues of ubiquitin results in diubiquitin or polyubiquitination. Shown are the most frequently detected ubiquitin chains linked through Lys⁶³ or Lys⁴⁸ of ubiquitin. Lys⁴⁸- or Lys⁶³-linked chains have closed and extended conformation, respectively, resulting in different mechanisms of recognition by ubiquitin binding domains (UBDs).