title: Structural basis of p21H-ras molecular switch inhibition by a neutralizing antibody.
abstract: The ras oncogene product p21 functions as a molecular switch in the early section of the signal transduction pathway that is involved in cell growth and differentiation. When the protein is in its GTP-complexed form it is active in signal transduction, whereas it is inactive in its GDP-complexed form. The transforming activity of p21ras is neutralized by the mouse monoclonal antibody Y13-259, possibly by preventing GDP-GTP exchange. A molecular model of the variable fragment of Y13-259 has been derived using a knowledge-based prediction approach and computer-assisted modeling techniques. An analysis of this model while complexed with p21ras/(GDP) indicated that the two molecular switch regions are constrained by complex formation. Antibody binding inhibits GDP-GTP exchange through a mechanism of steric hindrance. Having identified necessary bound sites for inhibition, and explored their electrostatic properties, it should be possible to proceed with the design of antibody mimics as therapeutic agents in cancer control.
authors: Department of Biochemistry, University College Dublin, Belfield, Republic of Ireland.
authors: W M
authors: WM
authors: Gallagher
authors: G H
authors: GH
authors: Grant
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex / Q000737:chemistry*; D003198:Computer Simulation; D007128:Immunoglobulin Fragments / Q000737:chemistry*; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry; D007147:Immunoglobulin Light Chains / Q000737:chemistry; D007135:Immunoglobulin Variable Region / Q000737:chemistry*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D011487:Protein Conformation; D016283:Proto-Oncogene Proteins p21(ras) / Q000737:chemistry* / Q000276:immunology; D017385:Sequence Homology
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007128:Immunoglobulin Fragments; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region; C055966:immunoglobulin Fv; D016283:Proto-Oncogene Proteins p21(ras)