RESUMO
IkappaB proteins associate with the transcription factor NF-kappaB via their ankyrin repeat domain. Bcl-3 is an unusual IkappaB protein because it is primarily nucleoplasmic and can lead to enhanced NF-kappaB-dependent transcription, unlike the prototypical IkappaB protein IkappaBalpha, which inhibits NF-kappaB activity by retaining it in the cytoplasm. Here we report the 1.9 A crystal structure of the ankyrin repeat domain of human Bcl-3 and compare it with that of IkappaBalpha bound to NF-kappaB. The two structures are highly similar over the central ankyrin repeats but differ in the N-terminal repeat and at the C-terminus, where Bcl-3 contains a seventh repeat in place of the acidic PEST region of IkappaBalpha. Differences between the two structures suggest why Bcl-3 differs from IkappaBalpha in selectivity towards various NF-kappaB species, why Bcl-3 but not IkappaBalpha can associate with its NF-kappaB partner bound to DNA, and why two molecules of Bcl-3 but only one of IkappaBalpha can bind to its NF-kappaB partner. Comparison of the two structures thus provides an insight into the functional diversity of IkappaB proteins.
Assuntos
Anquirinas/química , Proteínas I-kappa B , Proteínas Proto-Oncogênicas/química , Sequência de Aminoácidos , Proteína 3 do Linfoma de Células B , Sítios de Ligação , Cristalografia por Raios X , Citoplasma/metabolismo , Proteínas de Ligação a DNA/química , Humanos , Modelos Biológicos , Modelos Moleculares , Dados de Sequência Molecular , Inibidor de NF-kappaB alfa , NF-kappa B/química , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Sequências Repetitivas de Aminoácidos , Homologia de Sequência de Aminoácidos , Fatores de TranscriçãoRESUMO
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Assuntos
Depressão Pós-Parto/prevenção & controle , Inquéritos e Questionários , Escócia , Prevenção Primária , Testes PsicológicosRESUMO
We describe the crystal structure of d(GCGAATTCG) determined by x-ray diffraction at atomic resolution level (0.89 A). The duplex structure is practically identical to that described at 2.05 A resolution (Van Meervelt, L., Vlieghe, D., Dautant, A., Gallois, B., Précigoux, G., and Kennard, O. (1995) Nature 374, 742-744), however about half of the phosphate groups show multiple conformations. The crystal has three regions with different solvent structure. One of them contains several ordered Mg(+2) ions and can be considered as an ionic crystal. A second region is formed by a network of ordered water molecules with a polygonal organization that binds three duplexes. The third region is formed by channels of solvent in which very few ordered solvent molecules are visible. The less ordered phosphates are found facing this channel. The latter region provides a view of DNA with highly movable charges, both negative phosphates and counterions, without a precise location.
Assuntos
Conformação de Ácido Nucleico , Oligonucleotídeos/química , Solventes/química , Sequência de Bases , Modelos Moleculares , Água/químicaRESUMO
A detailed picture of hydration and counterion location in the B-DNA duplex d(GCGAATTCG) is presented. Detailed data have been obtained by single crystal x-ray diffraction at atomic resolution (0.89 A) in the presence of Mg(2+). The latter is the highest resolution ever obtained for a B-DNA oligonucleotide. Minor groove hydration is compared with that found in the Na(+) and Ca(2+) crystal forms of the related dodecamer d(CGCGAATTCGCG). High resolution data (1.45 A) of the Ca(2+) form obtained in our laboratory are used for that purpose. The central GAATTC has a very stable hydration spine identical in all cases, independent of duplex length and crystallization conditions (counterions, space group). However, the organization of the water molecules (tertiary and quaternary layers) associated with the central spine vary in each case.
