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.
Copyright © 2012 Elsevier Inc. All rights reserved.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing / chemistry*
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Adaptor Proteins, Signal Transducing / metabolism
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Anaphase-Promoting Complex-Cyclosome
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Binding Sites / physiology
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Carrier Proteins / chemistry*
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Carrier Proteins / metabolism
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Crystallography, X-Ray
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Cullin Proteins / chemistry*
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Cullin Proteins / metabolism
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Glomus Tumor / metabolism
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Humans
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Models, Chemical
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Mutagenesis / physiology
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Paraganglioma, Extra-Adrenal / metabolism
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Protein Binding / physiology
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Protein Folding
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Protein Structure, Tertiary / physiology
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Structure-Activity Relationship
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Substrate Specificity / physiology
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Ubiquitin-Conjugating Enzymes
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Ubiquitin-Protein Ligase Complexes / chemistry
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Ubiquitin-Protein Ligase Complexes / metabolism
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Ubiquitin-Protein Ligases / antagonists & inhibitors*
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Ubiquitin-Protein Ligases / chemistry*
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Ubiquitin-Protein Ligases / metabolism
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Ubiquitination / physiology*
Substances
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Adaptor Proteins, Signal Transducing
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Carrier Proteins
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Cullin 1
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Cullin Proteins
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GLMN protein, human
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RBX1 protein, human
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CDC34 protein, human
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Ubiquitin-Conjugating Enzymes
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Ubiquitin-Protein Ligase Complexes
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Anaphase-Promoting Complex-Cyclosome
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Ubiquitin-Protein Ligases