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CRYSTAL STRUCTURE OF AN IKBBETA/NF-KB P65 HOMODIMER COMPLEX
Structural highlights
FunctionTF65_MOUSE NF-kappa-B is a pleiotropic transcription factor present in almost all cell types and is the endpoint of a series of signal transduction events that are initiated by a vast array of stimuli related to many biological processes such as inflammation, immunity, differentiation, cell growth, tumorigenesis and apoptosis. NF-kappa-B is a homo- or heterodimeric complex formed by the Rel-like domain-containing proteins RELA/p65, RELB, NFKB1/p105, NFKB1/p50, REL and NFKB2/p52 and the heterodimeric p65-p50 complex appears to be most abundant one. The dimers bind at kappa-B sites in the DNA of their target genes and the individual dimers have distinct preferences for different kappa-B sites that they can bind with distinguishable affinity and specificity. Different dimer combinations act as transcriptional activators or repressors, respectively. NF-kappa-B is controlled by various mechanisms of post-translational modification and subcellular compartmentalization as well as by interactions with other cofactors or corepressors. NF-kappa-B complexes are held in the cytoplasm in an inactive state complexed with members of the NF-kappa-B inhibitor (I-kappa-B) family. In a conventional activation pathway, I-kappa-B is phosphorylated by I-kappa-B kinases (IKKs) in response to different activators, subsequently degraded thus liberating the active NF-kappa-B complex which translocates to the nucleus. NF-kappa-B heterodimeric p65-p50 and p65-c-Rel complexes are transcriptional activators. The NF-kappa-B p65-p65 complex appears to be involved in invasin-mediated activation of IL-8 expression (By similarity). The inhibitory effect of I-kappa-B upon NF-kappa-B the cytoplasm is exerted primarily through the interaction with p65. p65 shows a weak DNA-binding site which could contribute directly to DNA binding in the NF-kappa-B complex. Associates with chromatin at the NF-kappa-B promoter region via association with DDX1.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedWe report the crystal structure of a murine IkappaBbeta x NF-kappaB p65 homodimer complex. Crystallographic models were determined for two triclinic crystalline systems and refined against data at 2.5 and 2.1 A. The overall complex structure is similar to that of the IkappaBalpha.NF-kappaB p50/p65 heterodimer complex. One NF-kappaB p65 subunit nuclear localization signal clearly contacts IkappaBbeta, whereas a homologous segment from the second subunit of the homodimer is mostly solvent-exposed. The unique 47-amino acid insertion between ankyrin repeats three and four of IkappaBbeta is mostly disordered in the structure. Primary sequence analysis and differences in the mode of binding at the IkappaBbeta sixth ankyrin repeat and NF-kappaB p65 homodimer suggest a model for nuclear IkappaBbeta.NF-kappaB.DNA ternary complex formation. These unique structural features of IkappaBbeta may contribute to its ability to mediate persistent NF-kappaB activation. X-ray crystal structure of an IkappaBbeta x NF-kappaB p65 homodimer complex.,Malek S, Huang DB, Huxford T, Ghosh S, Ghosh G J Biol Chem. 2003 Jun 20;278(25):23094-100. Epub 2003 Apr 9. PMID:12686541[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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