Ubiquitin-RAS peptide extensions as substrates for farnesyl-protein transferase and carboxymethyltransferase

Protein expression using ubiquitin fusion and cleavage

Expressing proteins and polypeptides as fusions to ubiquitin offers the advantage of an often dramatic increase in yield, and the ability to produce any desired amino-terminal residue upon ubiquitin cleavage. The recent availability of cloned ubiquitin-cleaving enzymes has enhanced this technique for both bacterial and eukaryotic host systems.

Carboxy-terminal CVLS-sequence-specific protein farnesyltransferase from the eyes of the shrimp Penaeus japonicus: purification and characterization

Protein farnesyltransferase from the eyes of Penaeus japonicus farnesylates predominantly H-ras-specific carboxyl termini, with the sequence CVLS, but not the K-ras-specific sequence CVIM or the protein geranylgeranyltransferase-specific sequence CAIL. The purified protein farnesyltransferase from shrimp was found by immunoblotting and polyacrylamide gel electrophoresis under denaturing conditions to consist of subunits of Mr 49,000 and Mr 48,000. Since the active protein farnesyltransferase was found to have a relative mass of 100,000, the purified enzyme was deduced to be a heterodimer. The enzyme had an optimal pH of 6 and a K(m) of 14 +/- 1 microM with the synthetic peptide RTRCVLSH as the substrate. The enzyme was activated by Mn+2 and Mg+2 but inhibited by Ca+2 ions.