Activity-Based Probes Developed by Applying a Sequential Dehydroalanine Formation Strategy to Expressed Proteins Reveal α-Potential-Globin-Modulating Deubiquitinase

We report a general and novel semisynthetic strategy for the preparation of ubiquitinated protein-activity-based probes on the basis of sequential dehydroalanine formation on expressed proteins. We applied this approach to construct a physiologically and therapeutically relevant ubiquitinated alpha-globin probe, which was used for the enrichment and proteomic identification of alpha-globin-modulating deubiquitinases. We found USP15 as a potential deubiquitinase for the modulation of alpha-globin, an excess of which aggravates beta-thalassemia symptoms. This development opens new opportunities for activity-based-probe design to shed light on the important aspects underlying ubiquitination and deubiquitination in health and disease.