Insights into Ubiquitination from the Unique Clamp-like Binding of the RING E3 AO7 to the E2 UbcH5B.
J Biol Chem
; 290(51): 30225-39, 2015 Dec 18.
Article
en En
| MEDLINE
| ID: mdl-26475854
ABSTRACT
RING proteins constitute the largest class of E3 ubiquitin ligases. Unlike most RINGs, AO7 (RNF25) binds the E2 ubiquitin-conjugating enzyme, UbcH5B (UBE2D2), with strikingly high affinity. We have defined, by co-crystallization, the distinctive means by which AO7 binds UbcH5B. AO7 contains a structurally unique UbcH5B binding region (U5BR) that is connected by an 11-amino acid linker to its RING domain, forming a clamp surrounding the E2. The U5BR interacts extensively with a region of UbcH5B that is distinct from both the active site and the RING-interacting region, referred to as the backside of the E2. An apparent paradox is that the high-affinity binding of the AO7 clamp to UbcH5B, which is dependent on the U5BR, decreases the rate of ubiquitination. We establish that this is a consequence of blocking the stimulatory, non-covalent, binding of ubiquitin to the backside of UbcH5B. Interestingly, when non-covalent backside ubiquitin binding cannot occur, the AO7 clamp now enhances the rate of ubiquitination. The high-affinity binding of the AO7 clamp to UbcH5B has also allowed for the co-crystallization of previously described and functionally important RING mutants at the RING-E2 interface. We show that mutations having marked effects on function only minimally affect the intermolecular interactions between the AO7 RING and UbcH5B, establishing a high degree of complexity in activation through the RING-E2 interface.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Enzimas Ubiquitina-Conjugadoras
/
Ubiquitina-Proteína Ligasas
/
Ubiquitinación
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
2015
Tipo del documento:
Article