UbiQ-106 is a new and first of its kind activity based probe for Nedd8 E1, E2 and E3 ligases [Mulder et al. 2016]. It is based on the Nedd8 sequence in which the C-terminal Gly76 has been replaced by a dehydroalanine (Dha) residue. The N-terminus is labeled with biotin; an aminohexanoic acid (Ahx) linker is used to create extra space between the biotin and Nedd8 protein for efficient access of biotin binding entities. It has been prepared by total chemical synthesis and is therefore well-defined in terms of biotinylation site.
UbiQ-106 is processed in a native manner by E1, E2 and E3 ligases and during this process it forms an electrophilic intermediate that can react with the active site Cys residue of the E1, E2 and E3 enzyme, thereby creating a covalent bond (see figure).