title: Crystal Structures of Human MdmX (HdmX) in Complex with p53 Peptide Analogues Reveal Surprising Conformational Changes.
abstract: p53 tumor suppressor activity is negatively regulated through binding to the oncogenic proteins Hdm2 and HdmX. The p53 residues Leu(26), Trp(23), and Phe(19) are crucial to mediate these interactions. Inhibiting p53 binding to both Hdm2 and HdmX should be a promising clinical approach to reactivate p53 in the cancer setting, but previous studies have suggested that the discovery of dual Hdm2/HdmX inhibitors will be difficult. We have determined the crystal structures at 1.3 A of the N-terminal domain of HdmX bound to two p53 peptidomimetics without and with a 6-chlorine substituent on the indole (which binds in the same subpocket as Trp(23) of p53). The latter compound is the most potent peptide-based antagonist of the p53-Hdm2 interaction yet to be described. The x-ray structures revealed surprising conformational changes of the binding cleft of HdmX, including an "open conformation" of Tyr(99) and unexpected "cross-talk" between the Trp and Leu pockets. Notably, the 6-chloro p53 peptidomimetic bound with high affinity to both HdmX and Hdm2 (K(d) values of 36 and 7 nm, respectively). Our results suggest that the development of potent dual inhibitors for HdmX and Hdm2 should be feasible. They also reveal possible conformational states of HdmX, which should lead to a better prediction of its interactions with potential biological partners.
authors.affiliation: Novartis Institutes for BioMedical Research, CH-4002 Basel, Switzerland. joerg.kallen@novartis.com
authors.forename: Joerg
authors.initials: J
authors.lastname: Kallen
authors.forename: Arnaud
authors.initials: A
authors.lastname: Goepfert
authors.forename: Anke
authors.initials: A
authors.lastname: Blechschmidt
authors.forename: Aude
authors.initials: A
authors.lastname: Izaac
authors.forename: Martin
authors.initials: M
authors.lastname: Geiser
authors.forename: Gisele
authors.initials: G
authors.lastname: Tavares
authors.forename: Paul
authors.initials: P
authors.lastname: Ramage
authors.forename: Pascal
authors.initials: P
authors.lastname: Furet
authors.forename: Keiichi
authors.initials: K
authors.lastname: Masuya
authors.forename: Joanna
authors.initials: J
authors.lastname: Lisztwan
mesh_terms: D001665:Binding Sites / Q000502:physiology; D040761:Biomimetic Materials / Q000737:chemistry* / Q000378:metabolism; D018797:Cell Cycle Proteins; D018360:Crystallography, X-Ray; D006801:Humans; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D010455:Peptides; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2