Selective Recruitment of an E2∼Ubiquitin Complex by an E3 Ubiquitin Ligase*

Abstract Background: Rbx1/ROC1 is an E3 ligase adaptor protein that functions with the E2 enzyme CDC34. Results: NMR and biochemical data show that Rbx1/ROC1 binds CDC34∼ubiquitin 50-fold tighter than CDC34. Conclusion: Rbx1/ROC1 selectively recruits E2∼ubiquitin and releases the E2 after ubiquitin transfer. Significance: Direct evidence is shown for preferential recognition of an E2∼ubiquitin complex by an E3 ligase. Article type: Research Article Keywords: E3 Ubiquitin Ligase, Enzyme Mechanisms, Protein Complexes, Structural Biology, Ubiquitin Conjugating Enzyme (Ubc), Ubiquitination Authors: Donald E.