Chemical Synthesis of Natural Polyubiquitin Chains through Auxiliary-Mediated Ligation of an Expressed Ubiquitin Isomer.

An efficient method for the assembly of polyUb chains using auxiliary-modified Ub isomers is reported. This strategy takes advantages of auxiliary-mediated native chemical ligation between the distal Ub C-terminal hydrazide and the auxiliary of proximal Ub. Using removable protecting groups, Lys48-linked and Lys6-linked tri-Ub and even a mixed-linkage Lys6, Lys48-linked triUb in multimilligram quantities was made. These results demonstrate that this strategy yields natural polyubiquitin chains of desired length and linkage by using Ub isomer.