Abstract: A method for the preparation of synthetic peptide products containing up to about forty amino acid residues as ubiquitin-carboxyl terminal extensions expressed in procaryotic cells such as E. coli is disclosed. This is accomplished by cloning appropriate oligonucleotides encoding the desired peptide as a ubiquitin peptide extension gene, splicing the gene into an appropriate plasmid which, in turn is transformed into E. coli, or other appropriate procaryotic cells and inducing expression of the ubiquitin peptide fusion product. When expressed, the cells produce recoverable amounts of ubiquitin extended at its carboxyl terminus by the encoded carboxyl terminal extended peptide (CTEP). The peptide can be recovered as ubiquitin fused extension products (Ub-CTEP) or, alternatively, can be cleaved from the ubiquitin by an appropriate eucaryotic peptidase and purified.

Abstract: A method for the preparation of synthetic peptide products containing up to about forty amino acid residues as ubiquitin-carboxyl terminal extensions expressed in procaryotic cells such as E. coli is disclosed. This is accomplished by cloning appropriate oligonucleotides encoding the desired peptide as a ubiquitin peptide extension gene, splicing the gene into an appropriate plasmid which, in turn is transformed into E. coli, or other appropriate procaryotic cells and inducing expression of the ubiquitin peptide fusion product. When expressed, the cells produce recoverable amounts of ubiquitin extended at its carboxyl terminus by the encoded carboxyl terminal extended peptide (CTEP). The peptide can be recovered as ubiquitin fused extension products (Ub-CTEP) or, alternatively, can be cleaved from the ubiquitin by an appropriate eucaryotic peptidase and purified.

Abstract: A method for assaying for enzymes that modify peptide chains, such as protein kinases and enzymes which modify the C-terminus of the Ha-RAS protein, is defined. This is done by incubating an extract in which the enzyme being assayed for may be present contained in a reaction mixture. The reaction mixture is made up of a buffer solution, a ubiquitin peptide extension, wherein the peptide contains a sequence known to be modified by an agent in the presence of the enzyme being assayed for, and the agent known to modify the peptide extension when the enzyme is present. The incubation is stopped and the ubiquitin peptide extension is separated from the solution and analyzed for the presence of the agent modified peptide. The extent of peptide modification can be both qualitative and quantative of the enzyme being assayed for. Protein kinases can be assayed for using a ubiquitin pepide extension containing the sequence (SEQ ID NO:1), Ser-Glu-Glu-Glu-Glu-Glu in the presence of a phosphorylating agent.