title: NMR studies of the conformational change in human N-p21ras produced by replacement of bound GDP with the GTP analog GTP gamma S.
abstract: 1H-Detected 15N-edited NMR in solution was used to study the conformational differences between the GDP- and GTP gamma S-bound forms of human N-p21ras. The amide protons of 15N-labeled glycine and isoleucine were observed. Resonances were assigned to residues of particular interest, glycines-60 and -75 and isoleucines-21 and -36, by incorporating various 13C-labeled amino acids in addition to [15N]glycine and [15N]iosleucine and by replacing Mg2+ by Co2+. When GTP gamma S replaced GDP in the active site of p21ras, only 5 of the 14 glycine amide resonances show major shifts, indicating that the conformational effects are fairly localized. Responsive glycines-10, -12, -13, and -15 are in the active site. Gly-75, located at the far end of a conformationally-active loop and helix, also responds to substitution of GTP gamma S for GDP, while Gly-77 does not, supporting a role for Gly-75 as a swivel point for the conformational change. The amide proton resonances of isoleucines-36 and -21 and a third unidentified isoleucine also undergo major shifts upon replacement of GDP by GTP gamma S. Thus, the effector-binding loop containing Ile-36 is confirmed to be involved in the conformational change, and the alpha-helix containing Ile-21 is also shown to be affected.
authors.affiliation: Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
authors.forename: A F
authors.initials: AF
authors.lastname: Miller
authors.forename: M Z
authors.initials: MZ
authors.lastname: Papastavros
authors.forename: A G
authors.initials: AG
authors.lastname: Redfield
mesh_terms: D002247:Carbon Isotopes; D003035:Cobalt / Q000378:metabolism; D005998:Glycine; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006801:Humans; D007532:Isoleucine; D008274:Magnesium / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008433:Mathematics; D009587:Nitrogen Isotopes; D011485:Protein Binding; D011487:Protein Conformation; D016283:Proto-Oncogene Proteins p21(ras) / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011994:Recombinant Proteins; D007532:Isoleucine; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D003035:Cobalt; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D008274:Magnesium; D005998:Glycine