Structural insights into the mechanism and E2 specificity of the RBR E3 ubiquitin ligase HHARI

Nat Commun. 2017 Aug 8;8(1):211. doi: 10.1038/s41467-017-00272-6.

Abstract

RING-in-between-RING (RBR) ubiquitin (Ub) E3 ligases function with Ub E2s through a RING/HECT hybrid mechanism to conjugate Ub to target proteins. Here, we report the crystal structure of the RBR E3, HHARI, in complex with a UbcH7 ~ Ub thioester mimetic which reveals the molecular basis for the specificity of this cognate E2/RBR E3 pair. The structure also reveals mechanistically important conformational changes in the RING1 and UBA-like domains of HHARI that accompany UbcH7 ~ Ub binding and provides a molecular basis by which HHARI recruits E2 ~ Ub in an 'open' conformation. In addition to optimally functioning with an E2 that solely performs transthiolation, our data suggests that HHARI prevents spurious discharge of Ub from E2 to lysine residues by: (1) harboring structural elements that block E2 ~ Ub from adopting a 'closed' conformation and (2) participating in contacts to ubiquitin that promote an open E2 ~ Ub conformation.HHARI is a RING-in-between-RING (RBR) ubiquitin (Ub) E3 ligase. Here the authors present the crystal structure of HHARI with the UbcH7 ~ Ub thioester intermediate mimetic, which reveals that HHARI binds this E2 ~ Ub in an open conformation and explains the specificity of this cognate RBR E3/E2 pair.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Catalytic Domain
  • Humans
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Ubiquitin / genetics
  • Ubiquitin / metabolism
  • Ubiquitin-Conjugating Enzymes / genetics
  • Ubiquitin-Conjugating Enzymes / metabolism*
  • Ubiquitin-Protein Ligases

Substances

  • Carrier Proteins
  • Ubiquitin
  • UBE2L3 protein, human
  • Ubiquitin-Conjugating Enzymes
  • ARIH1 protein, human
  • Ubiquitin-Protein Ligases