The expression vectors pINIII-A and pINIII (Ipp p5) were used to construct plasmids which direct the synthesis in Escherichia coli of the Kirsten ras viral (v-Ki-ras) and human cellular (c-Ki-ras) oncogene products as fusion proteins containing 9 and 10 extra amino acids, respectively, at their N termini. Authenticity of the bacterially produced proteins was determined by immunoprecipitation and immunoblot analyses with ras-specific monoclonal antibodies. After induction with

more »

... galactopyranoside, the viral protein represented approximately 20% of the total cellular protein. The majority of the protein was found in the postsonication low-speed centrifugation pellet. The synthesized viral protein was active in GTP binding, as judged by autophosphorylation and photoaffinity labeling assays. 302 on May 4, 2020 by guest http://jvi.asm.org/ Downloaded from EXPRESSION OF KIRSTEN ras PROTEINS 303 transform JA221 cells. The A2 reading frame of the expres-