Identification of residues of the H-ras protein critical for functional interaction with guanine nucleotide exchange factors
| Autor: | Raymond D. Mosteller, Daniel Broek, Jaewon Han |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
DNA
Complementary Saccharomyces cerevisiae Proteins GTP' Saccharomyces cerevisiae Cell Cycle Proteins Hydroxylamine Oncogene Protein p21(ras) Hydroxylamines Guanosine Diphosphate Polymerase Chain Reaction Fungal Proteins Ras-GRF1 GTP-binding protein regulators GTP-Binding Proteins Humans Amino Acid Sequence Cloning Molecular Molecular Biology biology ras-GRF1 Binding protein Antibodies Monoclonal Cell Biology biology.organism_classification beta-Galactosidase Kinetics enzymes and coenzymes (carbohydrates) Genes ras Biochemistry Mutagenesis SOS1 Mutagenesis Site-Directed Guanine nucleotide exchange factor Guanosine Triphosphate biological phenomena cell phenomena and immunity Research Article Mutagens |
| Zdroj: | Molecular and Cellular Biology. 14:1104-1112 |
| ISSN: | 1098-5549 0270-7306 |
| DOI: | 10.1128/mcb.14.2.1104 |
| Popis: | Ras proteins are activated in vivo by guanine nucleotide exchange factors encoded by genes homologous to the CDC25 gene of Saccharomyces cerevisiae. We have taken a combined genetic and biochemical approach to probe the sites on Ras proteins important for interaction with such exchange factors and to further probe the mechanism of CDC25-catalyzed GDP-GTP exchange. Random mutagenesis coupled with genetic selection in S. cerevisiae was used to generate second-site mutations within human H-ras-ala15 which could suppress the ability of the Ala-15 substitution to block CDC25 function. We transferred these second-site suppressor mutations to normal H-ras and oncogenic H-rasVal-12 to test whether they induced a general loss of function or whether they selectively affected CDC25 interaction. Four highly selective mutations were discovered, and they affected the surface-located amino acid residues 62, 63, 67, and 69. Two lines of evidence suggested that these residues may be involved in binding to CDC25: (i) using the yeast two-hybrid system, we demonstrated that these mutants cannot bind CDC25 under conditions where the wild-type H-Ras protein can; (ii) we demonstrated that the binding to H-Ras of monoclonal antibody Y13-259, whose epitope has been mapped to residues 63, 65, 66, 67, 70, and 73, is blocked by the mouse sos1 and yeast CDC25 gene products. We also present evidence that the mechanism by which CDC25 catalyzes exchange is more involved than simply catalyzing the release of bound nucleotide and passively allowing nucleotides to rebind. Most critically, a complex of Ras and CDC25 protein, unlike free Fas protein, possesses significantly greater affinity for GTP than for GDP. Furthermore, the Ras CDC25 complex is more readily dissociated into free subunits by GTP than it is by GDP. Both of these results suggest a function for CDC25 in promoting the selective exchange of GTP for GDP. |
| Databáze: | OpenAIRE |
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