E2-RING expansion of the NEDD8 cascade confers specificity to cullin modification.
Publication Type:Journal Article
Source:Mol Cell, Volume 33, Issue 4, p.483-95 (2009)
Keywords:Amino Acid Sequence, Animals, Binding Sites, Cells, Cultured, Cullin Proteins, Mice, Models, Molecular, Molecular Sequence Data, NIH 3T3 Cells, Protein Conformation, Protein Folding, Ubiquitin-Protein Ligases, Ubiquitins
<p>Ubiquitin and ubiquitin-like proteins (UBLs) are directed to targets by cascades of E1, E2, and E3 enzymes. The largest ubiquitin E3 subclass consists of cullin-RING ligases (CRLs), which contain one each of several cullins (CUL1, -2, -3, -4, or -5) and RING proteins (RBX1 or -2). CRLs are activated by ligation of the UBL NEDD8 to a conserved cullin lysine. How is cullin NEDD8ylation specificity established? Here we report that, like UBE2M (also known as UBC12), the previously uncharacterized E2 UBE2F is a NEDD8-conjugating enzyme in vitro and in vivo. Biochemical and structural analyses indicate how plasticity of hydrophobic E1-E2 interactions and E1 conformational flexibility allow one E1 to charge multiple E2s. The E2s have distinct functions, with UBE2M/RBX1 and UBE2F/RBX2 displaying different target cullin specificities. Together, these studies reveal the molecular basis for and functional importance of hierarchical expansion of the NEDD8 conjugation system in establishing selective CRL activation.</p>