Allosteric regulation of E2:E3 interactions promote a processive ubiquitination machine.
RING finger proteins constitute the large majority of ubiquitin ligases (E3s) and function by interacting with ubiquitin-conjugating enzymes (E2s) charged with ubiquitin. How low-affinity RING-E2 interactions result in highly processive substrate ubiquitination is largely unknown. The RING E3, gp78, represents an excellent model to study this process. gp78 includes a high-affinity secondary binding region for its cognate E2, Ube2g2, the G2BR. The G2BR allosterically enhances RING:Ube2g2 binding and ubiquitination. Structural analysis of the RING:Ube2g2:G2BR complex reveals that a G2BR-induced conformational effect at the RING:Ube2g2 interface is necessary for enhanced binding of RING to Ube2g2 or Ube2g2 conjugated to Ub. This conformational effect and a key ternary interaction with conjugated ubiquitin are required for ubiquitin transfer. Moreover, RING:Ube2g2 binding induces a second allosteric effect, disrupting Ube2g2:G2BR contacts, decreasing affinity and facilitating E2 exchange. Thus, gp78 is a ubiquitination machine where multiple E2-binding sites coordinately facilitate processive ubiquitination.
Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA.
Ranabir
R
Das
Yu-He
YH
Liang
Jennifer
J
Mariano
Jess
J
Li
Tao
T
Huang
Aaren
A
King
Sergey G
SG
Tarasov
Allan M
AM
Weissman
Xinhua
X
Ji
R Andrew
RA
Byrd
D000494:Allosteric Regulation / Q000502:physiology*; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D060285:Receptors, Autocrine Motility Factor / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology*
D046912:Multiprotein Complexes; C471617:UBE2G2 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C555000:AMFR protein, human; D060285:Receptors, Autocrine Motility Factor