title: Quaternary structures of tumor suppressor p53 and a specific p53 DNA complex.
abstract: The homotetrameric tumor suppressor p53 consists of folded core and tetramerization domains, linked and flanked by intrinsically disordered segments that impede structure analysis by x-ray crystallography and NMR. Here, we solved the quaternary structure of human p53 in solution by a combination of small-angle x-ray scattering, which defined its shape, and NMR, which identified the core domain interfaces and showed that the folded domains had the same structure in the intact protein as in fragments. We combined the solution data with electron microscopy on immobilized samples that provided medium resolution 3D maps. Ab initio and rigid body modeling of scattering data revealed an elongated cross-shaped structure with a pair of loosely coupled core domain dimers at the ends, which are accessible for binding to DNA and partner proteins. The core domains in that open conformation closed around a specific DNA response element to form a compact complex whose structure was independently determined by electron microscopy. The structure of the DNA complex is consistent with that of the complex of four separate core domains and response element fragments solved by x-ray crystallography and contacts identified by NMR. Electron microscopy on the conformationally mobile, unbound p53 selected a minor compact conformation, which resembled the closed conformation, from the ensemble of predominantly open conformations. A multipronged structural approach could be generally useful for the structural characterization of the rapidly growing number of multidomain proteins with intrinsically disordered regions.
authors.affiliation: Medical Research Council Centre for Protein Engineering, Hills Road, Cambridge CB2 0QH, United Kingdom.
authors.forename: Henning
authors.initials: H
authors.lastname: Tidow
authors.forename: Roberto
authors.initials: R
authors.lastname: Melero
authors.forename: Efstratios
authors.initials: E
authors.lastname: Mylonas
authors.forename: Stefan M V
authors.initials: SM
authors.lastname: Freund
authors.forename: J Guenter
authors.initials: JG
authors.lastname: Grossmann
authors.forename: José María
authors.initials: JM
authors.lastname: Carazo
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Mikel
authors.initials: M
authors.lastname: Valle
authors.forename: Alan R
authors.initials: AR
authors.lastname: Fersht
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008854:Microscopy, Electron; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D013057:Spectrum Analysis; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D016159:Tumor Suppressor Protein p53; D004247:DNA