Analysis of guanine nucleotide bound to ras protein in PC12 cells.
The ras gene product (p21) specifically binds GDP or GTP. In analogy with the reaction mechanism of other GTP-binding proteins, only the GTP-bound conformation is believed to be the biologically active one. Previously, we reported that not only oncogenic p21(Val-12) but also proto-oncogenic p21(Gly-12) could induce morphological differentiation in rat pheochromocytoma PC12 cells when microinjected in the complexed form with GTP gamma S [(1987) Mol. Cell. Biol. 7, 4553-4556]. In the present report we transformed PC12 cells with the oncogenic ras gene placed under the metallothionein I promoter. It was found that the transformed cells, when induced with Cd2+, differentiated in the absence of NGF. Then we analyzed the guanine nucleotide bound to p21 in the intact PC12 cells. It was found that conditionally induced p21(Val-12) was mostly present in the GTP-bound form, whereas the endogenous p21(Gly-12) was in the GDP-bound form. These results indicate again that p21.GTP induces the morphological differentiation of PC12 cells.
D000818:Animals; D002461:Cell Line, Transformed; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007118:Immunoassay; D010673:Pheochromocytoma; D010957:Plasmids; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D051381:Rats; D014162:Transfection; D014407:Tumor Cells, Cultured
D006150:Guanine Nucleotides; D011518:Proto-Oncogene Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D016283:Proto-Oncogene Proteins p21(ras)