4IC3 image
Deposition Date 2012-12-09
Release Date 2012-12-19
Last Version Date 2023-11-08
Entry Detail
PDB ID:
4IC3
Keywords:
Title:
Crystal structure of the F495L mutant XIAP RING domain
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.78 Å
R-Value Free:
0.22
R-Value Work:
0.17
R-Value Observed:
0.17
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:E3 ubiquitin-protein ligase XIAP
Gene (Uniprot):XIAP
Mutations:F495L
Chain IDs:A, B
Chain Length:74
Number of Molecules:2
Biological Source:Homo sapiens
Primary Citation
Regulation of ubiquitin transfer by XIAP, a dimeric RING E3 ligase
Biochem.J. 450 629 638 (2013)
PMID: 23259674 DOI: 10.1042/BJ20121702

Abstact

RING domains of E3 ligases promote transfer of Ub (ubiquitin) from the E2~Ub conjugate to target proteins. In many cases interaction of the E2~Ub conjugate with the RING domain requires its prior dimerization. Using cross-linking experiments we show that E2 conjugated ubiquitin contacts the RING homodimer interface of the IAP (inhibitor of apoptosis) proteins, XIAP (X-linked IAP) and cIAP (cellular IAP) 2. Structural and biochemical analysis of the XIAP RING dimer shows that an aromatic residue at the dimer interface is required for E2~Ub binding and Ub transfer. Mutation of the aromatic residue abolishes Ub transfer, but not interaction with Ub. This indicates that nuleophilic attack on the thioester bond depends on precise contacts between Ub and the RING domain. RING dimerization is a critical activating step for the cIAP proteins; however, our analysis shows that the RING domain of XIAP forms a stable dimer and its E3 ligase activity does not require an activation step.

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