title: Mechanism of I kappa B alpha binding to NF-kappa B dimers.
abstract: X-ray crystal structures of the NF-kappa B.I kappa B alpha complex revealed an extensive and complex protein-protein interface involving independent structural elements present in both I kappa B alpha and NF-kappa B. In this study, we employ a gel electrophoretic mobility shift assay to assess and quantitate the relative contributions of the observed interactions toward overall complex binding affinity. I kappa B alpha preferentially binds to the p50/p65 heterodimer and p65 homodimer, with binding to p50 homodimer being significantly weaker. Our results indicate that the nuclear localization sequence and the region C-terminal to it of the NF-kappa B p65 subunit is a major contributor to NF-kappa B. I kappa B alpha complex formation. Additionally, there are no contacts between the corresponding nuclear localization signal tetrapeptide of p50 and I kappa B alpha. A second set of interactions involving the acidic C-terminal/PEST-like region of I kappa B alpha and the NF-kappa B p65 subunit N-terminal domain also contributes binding energy toward formation of the complex. This interaction is highly dynamic and nonspecific in nature, as shown by oxidative cysteine cross-linking. Phosphorylation of the C-terminal/PEST-like region by casein kinase II further enhances binding.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Phelps
authors.forename: L L
authors.initials: LL
authors.lastname: Sengchanthalangsy
authors.forename: T
authors.initials: T
authors.lastname: Huxford
authors.forename: G
authors.initials: G
authors.lastname: Ghosh
mesh_terms: D001665:Binding Sites; D019281:Dimerization; D004926:Escherichia coli; D006801:Humans; D020672:I-kappa B Proteins / Q000737:chemistry* / Q000378:metabolism; D016328:NF-kappa B / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D020672:I-kappa B Proteins; D016328:NF-kappa B