FBXO31 is a substrate adapter for the SCF-type ubiquitin ligase complex SCF/FBXO31 which ubiquitylates C-terminal amide-bearing proteins (CTAPs), thereby triggering their proteasomal degradation in human cells. Profiling of active cullin-RING ubiquitin E3 ligases was performed in naive or FBXO31 knockdown cell lines treated with hydrogen peroxide.