title: Structure of free MDM2 N-terminal domain reveals conformational adjustments that accompany p53-binding.
abstract: Critical to the inhibitory action of the oncogene product, MDM2, on the tumour suppressor, p53, is association of the N-terminal domain of MDM2 (MDM2N) with the transactivation domain of p53. The structure of MDM2N was previously solved with a p53-derived peptide, or small-molecule ligands, occupying its binding cleft, but no structure of the non-liganded MDM2N (i.e. the apo-form) has been reported. Here, we describe the solution structure and dynamics of apo-MDM2N and thus reveal the nature of the conformational changes in MDM2N that accompany binding of p53. The new structure suggests that p53 effects displacement of an N-terminal segment of apo-MDM2N that occludes access to the shallow end of the p53-binding cleft. MDM2N must also undergo an expansion upon binding, achieved through a rearrangement of its two pseudosymetrically related sub-domains resulting in outward displacements of the secondary structural elements that comprise the walls and floor of the p53-binding cleft. MDM2N becomes more rigid and stable upon binding p53. Conformational plasticity of the binding cleft of apo-MDM2N could allow the parent protein to bind specifically to several different partners, although, to date, all the known liganded structures of MDM2N are highly similar to one another. The results indicate that the more open conformation of the binding cleft of MDM2N observed in structures of complexes with small molecules and peptides is a more suitable one for ligand discovery and optimisation.
authors.affiliation: Schools of Chemistry and Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JR, UK.
authors.forename: Stanislava
authors.initials: S
authors.lastname: Uhrinova
authors.forename: Dusan
authors.initials: D
authors.lastname: Uhrin
authors.forename: Helen
authors.initials: H
authors.lastname: Powers
authors.forename: Kathryn
authors.initials: K
authors.lastname: Watt
authors.forename: Daniella
authors.initials: D
authors.lastname: Zheleva
authors.forename: Peter
authors.initials: P
authors.lastname: Fischer
authors.forename: Campbell
authors.initials: C
authors.lastname: McInnes
authors.forename: Paul N
authors.initials: PN
authors.lastname: Barlow
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D030562:Databases, Protein; D006801:Humans; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014981:Xenopus
chemical_list: D008024:Ligands; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2