No abstract

The purified p21src protein of Harvey sarcoma virus shows a guanine nucleotide-binding activity and, in addition, at elevated temperature an autophosphorylating activity at a threonine residue using as phosphoryl donor GTP or dGTP but not ATP or dATP. These biochemical activities are unique among those associated with transforming proteins of RNA-containing or DNA-containing tumour viruses.

We have recently described an intracellular protein, p21, in nonproducer cells transformed by either the Kirsten (Ki-MSV) or Harvey (Ha-MSV) strain of murine sarcoma virus (Shih et al., Virology, in press). The p21 is phosphorylated and has been shown to be coded for by either Ki-MSV or Ha-MSV. In this report, we compare the thermal stability of the newly synthesized [35S]methioninelabeled p21 in cells transformed by the wild-type Ki-MSV or by a mutant of Ki-MSV(ts 371) which is temperature sensitive in a viral function required for the maintenance of several properties of the transformed phenotype. The immuno

MATERIALS AND METHODS Cells and viruses. All cells were grown in Dulbecco-Vogt modified Eagle minimal essential medium (DMEM) containing 10% fetal calf serum. The following Ha-MuSV-transformed nonproducer cell lines were used in this study: Ha-C127, a Ha-MuSV-trans-253