title: Hydrodynamic bead modelling of the 2:1 p50-IkappaBgamma complex.
abstract: NFkappaB is an important and ubiquitous transcription factor formed by various homo- and heterodimers of the NFkappaB family. The active transcription factor regulates genes involved in immune, inflammatory and survival responses. Specificity in gene regulation is achieved, at least in part, by the distinct DNA binding preferences of the various homo- and heterodimers and by the complex pathways that lead to signal-induced degradation of the IkappaB inhibitors. Analytical ultracentrifugation and hydrodynamic bead modelling were used to model the solution structures of the NFkappaB family member p50, its inhibitor IkappaBgamma and their complex. Sedimentation equilibrium (SE) and sedimentation velocity (SV) data show that p50 is a dimer in solution with a sedimentation coefficient consistent with a conformation intermediate between the closed conformation observed in the crystal structure of the p50 (N-terminal domain)-p65 heterodimer complexed with IkappaBalpha and the open conformation adopted by p50 when bound to DNA. SE and SV data show that IkappaBgamma is a monomer in solution and is prone to aggregation over time. p50 forms a 2:1 stoichiometric complex with IkappaBgamma in solution with a sedimentation coefficient consistent with a closed conformation for the p50 dimer.
authors.affiliation: Biomolecular Sciences Building, School of Biology, University of St. Andrews, The North Haugh, St. Andrews KY16 9ST, Scotland, UK.
authors.forename: Michaela
authors.initials: M
authors.lastname: Smolle
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Hay
authors.forename: Olwyn
authors.initials: O
authors.lastname: Byron
mesh_terms: D001288:Attention; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D005786:Gene Expression Regulation; D020672:I-kappa B Proteins / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008970:Molecular Weight; D016328:NF-kappa B / Q000737:chemistry*; D052002:NF-kappa B p50 Subunit; D010316:Particle Size; D011487:Protein Conformation; D012996:Solutions; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism; D014461:Ultracentrifugation
chemical_list: D020672:I-kappa B Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D012996:Solutions; D014157:Transcription Factors; D004247:DNA