title: Conformation of guanosine 5'-diphosphate as bound to a human c-Ha-ras mutant protein: a nuclear Overhauser effect study.
abstract: 1H NMR spectra of a GDP/GTP-binding domain of human c-Ha-ras gene product (residues 1-171) in which glutamine-61 was replaced by leucine [ras(L61/1-171) protein] were analyzed. By one-dimensional and two-dimensional homonuclear Hartmann-Hahn spectroscopy and nuclear Overhauser effect (NOE) spectroscopy of the complex of the ras(L61/1-171) protein and GDP, the ribose H1', H2', H3', and H4' proton resonances of the bound GDP were identified. The guanine H8 proton resonance of the bound GDP was identified by substituting [8-2H]GDP for GDP. The dependences of the H1' and H8 proton resonance intensities on the duration of irradiation of the H1', H2', H3', and H8 protons were measured. By numerical simulation of these time-dependent NOE profiles, the conformation of the protein-bound GDP was elucidated; the guanosine moiety takes the anti form about the N-glycosidic bond with a dihedral angle of chi = -124 +/- 2 degrees and the ribose ring takes the C2'-endo form. Such an analysis of the conformation of a guanine nucleotide as bound to a GTP-binding protein will be useful for further studies on the molecular mechanism of the conformational activation of ras proteins on ligand substitution of GDP with GTP.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
authors.forename: J M
authors.initials: JM
authors.lastname: Ha
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.forename: G
authors.initials: G
authors.lastname: Kawai
authors.forename: T
authors.initials: T
authors.lastname: Miyazawa
authors.forename: K
authors.initials: K
authors.lastname: Miura
authors.forename: E
authors.initials: E
authors.lastname: Ohtsuka
authors.forename: S
authors.initials: S
authors.lastname: Noguchi
authors.forename: S
authors.initials: S
authors.lastname: Nishimura
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D001483:Base Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D006150:Guanine Nucleotides; D011518:Proto-Oncogene Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)