Identification of a precursor in the biosynthesis of the p21 transforming protein of harvey murine sarcoma virus.
AUTOR(ES)
Shih, T Y
RESUMO
The p21 transforming protein coded for by the v-ras gene of Harvey murine sarcoma virus (Ha-MuSV) migrates as a doublet band between 21,000 and 23,000 daltons during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The lower band of the doublet is designated p21, and the upper band is designated pp21 since it comigrates with the phosphorylated form of p21. By pulse-labeling with [35S] methionine, we detected a p21 precursor, pro-p21, which migrated as if it was approximately 1,000 daltons larger than p21. The precursor-product relationship was established by pulse-chase experiments with [25S] methionine in the presence of 100 micrograms of cycloheximide per ml, which inhibited all de novo protein biosynthesis. Within 4 h, pro-p21 was completely chased into p21, and during the next 24 h pp21 accumulated. Thus, formation of pp21 from p21 did not require de novo protein synthesis. By subcellular fractionation into cytosol amd membrane fractions, we found that pro-p21 was synthesized in a non-membrane-bound state and that shortly after its complete synthesis, the p21 product was associated with the membrane fraction. By selective cleavage of p21 at a unique aspartic acid-proline residue with 70% formic acid or with Staphylococcus aureus V8 protease, we found that the intramolecular site of pro-p21 processing was located in the C-terminal portion of the pro-p21 molecule. The possibilities that the precursor was involved in the assembly of p21 into the plasma membrane and, alternatively, that the processing was a step in the activation of p21 biochemical activities are discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=256066Documentos Relacionados
- Further genetic localization of the transforming sequences of the p21 v-ras gene of Harvey murine sarcoma virus.
- Harvey murine sarcoma virus p21 ras protein: biological and biochemical significance of the cysteine nearest the carboxy terminus.
- Monoclonal antibodies to the p21 products of the transforming gene of Harvey murine sarcoma virus and of the cellular ras gene family.
- Analysis of two divergent rat genomic clones homologous to the transforming gene of Harvey murine sarcoma virus.
- p21 of Kirsten murine sarcoma virus is thermolabile in a viral mutant temperature sensitive for the maintenance of transformation.