Activity-based Pull-down of Proteolytic Standard and Immunoproteasome Subunits

Abstract

Activity-based probes (ABP) are small organic molecules that irreversibly bind to the active center of a specific enzyme family and may be coupled to a fluorophore or an affinity tag (Li et al., 2013). Here, we describe a method to pull-down active catalytic standard and immunoproteasome subunits in cell lysates using the biotinylated, proteasome-specific ABP Biotin-Epoxomicin (Bio-EP). Covalent labeling of the active catalytic subunits with Bio-EP is followed by a pull-down using streptavidin-coated beads. After elution from the beads, enriched subunits may be detected via Western blot, tandem mass spectrometry (Li et al., 2013), or alternative techniques.