title: Interaction of a novel GDP exchange inhibitor with the Ras protein.
abstract: Mutated, tumorigenic Ras is present in a variety of human tumors. Compounds that inhibit tumorigenic Ras function may be useful in the treatment of Ras-related tumors. The interaction of a novel GDP exchange inhibitor (SCH-54292) with the Ras-GDP protein was studied by NMR spectroscopy. The binding of the inhibitor to the Ras protein was enhanced at low Mg2+ concentrations, which enabled the preparation of a stable complex for NMR study. To understand the enhanced inhibitor binding and the increased GDP dissociation rates of the Ras protein, the conformational changes of the Ras protein at low Mg2+ concentrations was investigated using two-dimensional 1H-15N HSQC experiments. The Ras protein existed in two conformations in slow exchange on the NMR time scale under such conditions. The conformational changes mainly occurred in the GDP binding pocket, in the switch I and the switch II regions, and were reversible. The Ras protein resumed its regular conformation after an excess amount of Mg2+ was added. A model of the inhibitor in complex with the Ras-GDP protein was derived from intra- and intermolecular NOE distance constraints, and revealed that the inhibitor bound to the critical switch II region of the Ras protein.
authors.affiliation: Agouron Pharmaceuticals, San Diego, California 92121, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Ganguly
authors.forename: Y S
authors.initials: YS
authors.lastname: Wang
authors.forename: B N
authors.initials: BN
authors.lastname: Pramanik
authors.forename: R J
authors.initials: RJ
authors.lastname: Doll
authors.forename: M E
authors.initials: ME
authors.lastname: Snow
authors.forename: A G
authors.initials: AG
authors.lastname: Taveras
authors.forename: S
authors.initials: S
authors.lastname: Remiszewski
authors.forename: D
authors.initials: D
authors.lastname: Cesarz
authors.forename: J
authors.initials: J
authors.lastname: del Rosario
authors.forename: B
authors.initials: B
authors.lastname: Vibulbhan
authors.forename: J E
authors.initials: JE
authors.lastname: Brown
authors.forename: P
authors.initials: P
authors.lastname: Kirschmeier
authors.forename: E C
authors.initials: EC
authors.lastname: Huang
authors.forename: L
authors.initials: L
authors.lastname: Heimark
authors.forename: A
authors.initials: A
authors.lastname: Tsarbopoulos
authors.forename: V M
authors.initials: VM
authors.lastname: Girijavallabhan
authors.forename: R M
authors.initials: RM
authors.lastname: Aust
authors.forename: E L
authors.initials: EL
authors.lastname: Brown
authors.forename: D M
authors.initials: DM
authors.lastname: DeLisle
authors.forename: S A
authors.initials: SA
authors.lastname: Fuhrman
authors.forename: T F
authors.initials: TF
authors.lastname: Hendrickson
authors.forename: C R
authors.initials: CR
authors.lastname: Kissinger
authors.forename: R A
authors.initials: RA
authors.lastname: Love
authors.forename: W A
authors.initials: WA
authors.lastname: Sisson
authors.forename: S E
authors.initials: SE
authors.lastname: Webber
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003198:Computer Simulation; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009010:Monte Carlo Method; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D013449:Sulfonamides / Q000737:chemistry / Q000378:metabolism*; D020663:ras Guanine Nucleotide Exchange Factors; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D005960:Glucosides; D020662:Guanine Nucleotide Exchange Factors; D046911:Macromolecular Substances; D011506:Proteins; C107861:SCH 54292; D013449:Sulfonamides; D020663:ras Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate; D018631:ras Proteins; D008274:Magnesium