Download MendeleySelective recruitment of an e2~ubiquitin complex by an e3 ubiquitin ligase.
Spratt, D.E., Wu, K., Kovacev, J., Pan, Z.Q., Shaw, G.S.(2012) J Biol Chem 287: 17374-17385
- PubMed: 22433864
- DOI: https://doi.org/10.1074/jbc.M112.353748
- Primary Citation of Related Structures:
2LGV - PubMed Abstract:
RING E3 ligases are proteins that must selectively recruit an E2-conjugating enzyme and facilitate ubiquitin transfer to a substrate. It is not clear how a RING E3 ligase differentiates a naked E2 enzyme from the E2∼ubiquitin-conjugated form or how this is altered upon ubiquitin transfer. RING-box protein 1 (Rbx1/ROC1) is a key protein found in the Skp1/Cullin-1/F-box (SCF) E3 ubiquitin ligase complex that functions with the E2 ubiquitin conjugating enzyme CDC34. The solution structure of Rbx1/ROC1 revealed a globular RING domain (residues 40-108) stabilized by three structural zinc ions (root mean square deviation 0.30 ± 0.04 Å) along with a disordered N terminus (residues 12-39). Titration data showed that Rbx1/ROC1 preferentially recruits CDC34 in its ubiquitin-conjugated form and favors this interaction by 50-fold compared with unconjugated CDC34. Furthermore, NMR and biochemical assays identified residues in helix α2 of Rbx1/ROC1 that are essential for binding and activating CDC34∼ubiquitin for ubiquitylation. Taken together, this work provides the first direct structural and biochemical evidence showing that polyubiquitylation by the RING E3 ligase Rbx1/ROC1 requires the preferential recruitment of an E2∼ubiquitin complex and subsequent release of the unconjugated E2 protein upon ubiquitin transfer to a substrate or ubiquitin chain.
Organizational Affiliation:
Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
