title: E2 interaction and dimerization in the crystal structure of TRAF6.
abstract: Tumor necrosis factor (TNF) receptor-associated factor (TRAF)-6 mediates Lys63-linked polyubiquitination for NF-kappaB activation via its N-terminal RING and zinc finger domains. Here we report the crystal structures of TRAF6 and its complex with the ubiquitin-conjugating enzyme (E2) Ubc13. The RING and zinc fingers of TRAF6 assume a rigid, elongated structure. Interaction of TRAF6 with Ubc13 involves direct contacts of the RING and the preceding residues, and the first zinc finger has a structural role. Unexpectedly, this region of TRAF6 is dimeric both in the crystal and in solution, different from the trimeric C-terminal TRAF domain. Structure-based mutagenesis reveals that TRAF6 dimerization is crucial for polyubiquitin synthesis and autoubiquitination. Fluorescence resonance energy transfer analysis shows that TRAF6 dimerization induces higher-order oligomerization of full-length TRAF6. The mismatch of dimeric and trimeric symmetry may provide a mode of infinite oligomerization that facilitates ligand-dependent signal transduction of many immune receptors.
authors.affiliation: Weill Medical College of Cornell University, New York, New York, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yin
authors.forename: Su-Chang
authors.initials: SC
authors.lastname: Lin
authors.forename: Betty
authors.initials: B
authors.lastname: Lamothe
authors.forename: Miao
authors.initials: M
authors.lastname: Lu
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Lo
authors.forename: Gregory
authors.initials: G
authors.lastname: Hura
authors.forename: Lixin
authors.initials: L
authors.lastname: Zheng
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Rich
authors.forename: Alejandro D
authors.initials: AD
authors.lastname: Campos
authors.forename: David G
authors.initials: DG
authors.lastname: Myszka
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lenardo
authors.forename: Bryant G
authors.initials: BG
authors.lastname: Darnay
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
mesh_terms: D018360:Crystallography, X-Ray; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D011487:Protein Conformation; D055503:Protein Multimerization; D054829:RING Finger Domains; D048029:TNF Receptor-Associated Factor 6 / Q000737:chemistry*; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry*; D054875:Ubiquitination; D016335:Zinc Fingers
chemical_list: D048029:TNF Receptor-Associated Factor 6; C471607:UBE2N protein, human; D044763:Ubiquitin-Conjugating Enzymes