New semi-synthesis of ubiquitin C-terminal conjugate with 7-amino-4-methylcoumarin†

The ligation of peptide hydrazides at a Gly site carrying a removal auxiliary was found to be an efficient process. This technology was successfully used for the synthesis of ubiquitin C-terminal conjugates. Recombinant Ub(1–75)-NHNH2 was prepared through the hydrozinolysis of the Ub(1–75)-intein fusion protein. It was ligated with a glycine derivative modified with an acid-sensitive thiol auxiliary. The final acid treatment produced the desired bioactive ubiquitin conjugates in practical quantities. Thus, the method described here extends the protocols of expressed protein ligation. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.