In earlier studies, we molecularly cloned a normal cellular gene, c-rasH-1, homologous to the v-ras oncogene of Harvey murine sarcoma virus (v-
rasH). By ligating a type c retroviral promotor to c-rasH-1, we could transform NIH 3T3 cells with the c-rasH-1 gene. The transformed cells contained high levels of a p21
protein coded for by the c-rasH-1 gene. In the current studies, we have purified extensively both v-
rasH p21 and c-
rasH p21 and compared the in vivo and in vitro biochemical properties of both these p21 molecules. The p21
proteins coded for by v-
rasH and c-rasH-1 shared certain properties: each
protein was synthesized as a precursor
protein which subsequently became bound to the inner surface of the plasma membrane; each
protein was associated with
guanine nucleotide-binding activity, a property which copurified with p21 molecules on a high-pressure liquid chromatography molecular sizing column. In some other properties, the v-
rasH and c-
rasH p21
proteins differed. In vivo, approximately 20 to 30% of v-
rasH p21 molecules were in the form of
phosphothreonine-containing pp21 molecules, whereas in vivo only a minute fraction of c-rasH-1 p21 contained
phosphate, and this
phosphate was found on a
serine residue. v-
rasH pp21 molecules with an authentic
phosphothreonine peptide could be synthesized in vitro in an autophosphorylation reaction in which the gamma
phosphate of
GTP was transferred to v-
rasH p21. No autophosphorylating activity was associated with purified c-rasH-1 p21 in vitro. The results indicate a major qualitative difference between the p21
proteins coded for by v-
rasH and c-rasH-1. The p21 coded for by a mouse-derived oncogenic virus, BALB murine
sarcoma virus, resembled the p21 coded for by c-rasH-1 in that it bound
guanine nucleotides but did not label appreciably with 32Pi. The forms of p21 coded for by other members of the ras gene family were compared, and the results indicate that the
guanine nucleotide-binding activity is common to p21 molecules coded for by all known members of the ras gene family.