Competitive binding of UBPY and ubiquitin to the STAM2 SH3 domain revealed by NMR

► The SH3 domain of STAM2 binds ubiquitin and constitutes the third ubiquitin binding domain of STAM2. ► UBPY competes with ubiquitin for binding to the SH3 domain of STAM2. ► The binding of UBPY and ubiquitin to the SH3 domain does not require the UIM domain of the STAM2 protein. ► The SH3 domain of STAM2 could be involved in cargo concentration at the ESCRT-0 level.