title: X-ray crystal structure of an IkappaBbeta x NF-kappaB p65 homodimer complex.
abstract: We 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0359, USA.
authors.forename: Shiva
authors.initials: S
authors.lastname: Malek
authors.forename: De-Bin
authors.initials: DB
authors.lastname: Huang
authors.forename: Tom
authors.initials: T
authors.lastname: Huxford
authors.forename: Sankar
authors.initials: S
authors.lastname: Ghosh
authors.forename: Gourisankar
authors.initials: G
authors.lastname: Ghosh
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray / Q000379:methods; D004247:DNA / Q000737:chemistry; D019281:Dimerization; D020672:I-kappa B Proteins / Q000737:chemistry*; D008958:Models, Molecular; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012680:Sensitivity and Specificity; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D051996:Transcription Factor RelA
chemical_list: C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA