5iea | pdb_00005iea
TRIM5 B-box2 and coiled-coil chimera
Structural highlights
Function[TRIM5_MACMU] Capsid-specific restriction factor that prevents infection from non-host-adapted retroviruses. Blocks viral replication early in the life cycle, after viral entry but before reverse transcription. In addition to acting as a capsid-specific restriction factor, also acts as a pattern recognition receptor that activates innate immune signaling in response to the retroviral capsid lattice. Binding to the viral capsid triggers its E3 ubiquitin ligase activity, and in concert with the heterodimeric ubiquitin conjugating enzyme complex UBE2V1-UBE2N (also known as UBC13-UEV1A complex) generates 'Lys-63'-linked polyubiquitin chains, which in turn are catalysts in the autophosphorylation of the MAP3K7/TAK1 complex (includes TAK1, TAB2, and TAB3). Activation of the MAP3K7/TAK1 complex by autophosphorylation results in the induction and expression of NF-kappa-B and MAPK-responsive inflammatory genes, thereby leading to an innate immune response in the infected cell. Restricts infection by human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV-agm).[1] [2] [3] Publication Abstract from PubMedRestriction factors and pattern recognition receptors are important components of intrinsic cellular defenses against viral infection. Mammalian TRIM5alpha proteins are restriction factors and receptors that target the capsid cores of retroviruses and activate ubiquitin-dependent antiviral responses upon capsid recognition. Here, we report crystallographic and functional studies of the TRIM5alpha B-box 2 domain, which mediates higher-order assembly of TRIM5 proteins. The B-box can form both dimers and trimers, and the trimers can link multiple TRIM5alpha proteins into a hexagonal net that matches the lattice arrangement of capsid subunits and enables avid capsid binding. Two modes of conformational flexibility allow TRIM5alpha to accommodate the variable curvature of retroviral capsids. B-box mediated interactions also modulate TRIM5alpha's E3 ubiquitin ligase activity, by stereochemically restricting how the N-terminal RING domain can dimerize. Overall, these studies define important molecular details of cellular recognition of retroviruses, and how recognition links to downstream processes to disable the virus. Mechanism of B-box 2 domain-mediated higher-order assembly of the retroviral restriction factor TRIM5alpha.,Wagner JM, Roganowicz MD, Skorupka K, Alam SL, Christensen DE, Doss GL, Wan Y, Frank GA, Ganser-Pornillos BK, Sundquist WI, Pornillos O Elife. 2016 Jun 2;5. pii: e16309. doi: 10.7554/eLife.16309. PMID:27253059[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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