Oligomeric structure of p21 ras proteins as determined by radiation inactivation

• Published in: The Journal of biological chemistry Vol. 263; no. 20; pp. 9853 - 9858
• Main Authors: Santos, E, Nebreda, A R, Bryan, T, Kempner, E S
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 15.07.1988; American Society for Biochemistry and Molecular Biology
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Cell Line, Transformed; Cell Membrane - metabolism; Dithiothreitol - pharmacology; Edetic Acid - pharmacology; Electrophoresis, Polyacrylamide Gel; Energy Transfer; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; genes; Guanosine Triphosphate - metabolism; Guanosine Triphosphate - pharmacology; Holoproteins; Immunosorbent Techniques; Macromolecular Substances; Membrane Proteins; Molecular Weight; Other proteins; Proteins; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins - radiation effects; Proto-Oncogene Proteins p21(ras); radiation; Cell culture; Signal transduction; GTP; Immunoprecipitation reaction; Gel electrophoresis; Molecular model; Oncoprotein; Onc gene; Inactivation; Monomer; Oligomer
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)81595-8

Using radiation inactivation we determined that p21 ras proteins exhibit an oligomeric target size when assayed both structurally and functionally. Similar target sizes of p21 in ras-transformed cells and in purified preparations of the protein suggested that its structure is homo-oligomeric. p21 monomers were destroyed by radiation with the same target size as the GTP binding activity, indicating the occurrence of a tight association allowing energy transfer between the monomers. Irradiation in the presence of GTP, dithiothreitol, or EDTA did not change the target size. Normal (Gly12) and transforming (Lys12) forms of the protein exhibited similar target sizes. The homo-oligomeric structure suggests that p21 ras proteins do not conform to the structure of monomeric alpha subunits in classical G proteins (alpha beta gamma heterotrimers) and establishes similarities with other homo-oligomeric proteins (such as Escherichia coli CRP) which acquire the active conformation through subunit reorientation upon nucleotide binding.