Autophosphorylation of v-Ha-ras p21 is modulated by amino acid residue 12.
- 1 May 1984
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 81 (9), 2674-2678
- https://doi.org/10.1073/pnas.81.9.2674
Abstract
The 21,000-dalton protein (p21) encoded by the ras oncogene of Harvey murine sarcoma virus (v-Ha-ras) becomes phosphorylated (pp21) in vivo and in vitro on threonine residue 59. p21 molecules encoded by cellular ras genes (c-Ha-ras-1) contain an alanine at position 59, and thus these p21 molecules are not phosphorylated. In this investigation, recombinant ras genes were constructed between the 5'' p21 coding region of normal (EC) or oncogenically activated (EJ) human c-Ha-ras-1 and the 3'' p21 coding region of v-Ha-ras to generate p21 molecules containing a threonine phosphoacceptor site at position 59 and a glycine (EC/v-Ha) or valine (EJ/v-Ha) at residue 12. In transformed NIH 3T3 mouse fibroblast cells labeled with [35S]methionine, the ratio of pp21 to p21 was strikingly modulated by the amino acid at residue 12. v-Ha-ras p21 has an arginine at position 12 and 24% of total p21 was in the phosphorylated form. A glycine at residue 12 decreased the amount of pp21 to 14% of total p21, and a valine at residue12 dramatically increased this value to 50%. In vitro, the valine form of p21 had 2.4- and 2.7-fold greater autophosphorylating activity than the glycine and arginine forms of p21, respectively, using [.gamma.-32P]GTP as phosphate donor, but the 3 p21 species had similar Km values for GTP (0.20-0.27 .mu.M). Evidently, a biochemical activity of p21 distinguishes between previously observed biological differences of normal and activated human ras genes.This publication has 29 references indexed in Scilit:
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