Structure of a glomulin-RBX1-CUL1 complex: inhibition of a RING E3 ligase through masking of its E2-binding surface

Mol Cell. 2012 Aug 10;47(3):371-82. doi: 10.1016/j.molcel.2012.05.044. Epub 2012 Jun 28.

Abstract

The approximately 300 human cullin-RING ligases (CRLs) are multisubunit E3s in which a RING protein, either RBX1 or RBX2, recruits an E2 to catalyze ubiquitination. RBX1-containing CRLs also can bind Glomulin (GLMN), which binds RBX1's RING domain, regulates the RBX1-CUL1-containing SCF(FBW7) complex, and is disrupted in the disease Glomuvenous Malformation. Here we report the crystal structure of a complex between GLMN, RBX1, and a fragment of CUL1. Structural and biochemical analyses reveal that GLMN adopts a HEAT-like repeat fold that tightly binds the E2-interacting surface of RBX1, inhibiting CRL-mediated chain formation by the E2 CDC34. The structure explains the basis for GLMN's selectivity toward RBX1 over RBX2, and how disease-associated mutations disrupt GLMN-RBX1 interactions. Our study reveals a mechanism for RING E3 ligase regulation, whereby an inhibitor blocks E2 access, and raises the possibility that other E3s are likewise controlled by cellular proteins that mask E2-binding surfaces to mediate inhibition.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / chemistry*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Anaphase-Promoting Complex-Cyclosome
  • Binding Sites / physiology
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism
  • Crystallography, X-Ray
  • Cullin Proteins / chemistry*
  • Cullin Proteins / metabolism
  • Glomus Tumor / metabolism
  • Humans
  • Models, Chemical
  • Mutagenesis / physiology
  • Paraganglioma, Extra-Adrenal / metabolism
  • Protein Binding / physiology
  • Protein Folding
  • Protein Structure, Tertiary / physiology
  • Structure-Activity Relationship
  • Substrate Specificity / physiology
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligase Complexes / chemistry
  • Ubiquitin-Protein Ligase Complexes / metabolism
  • Ubiquitin-Protein Ligases / antagonists & inhibitors*
  • Ubiquitin-Protein Ligases / chemistry*
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination / physiology*

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Cullin 1
  • Cullin Proteins
  • GLMN protein, human
  • RBX1 protein, human
  • CDC34 protein, human
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligase Complexes
  • Anaphase-Promoting Complex-Cyclosome
  • Ubiquitin-Protein Ligases

Supplementary concepts

  • Glomus vagale tumors

Associated data

  • PDB/4F52