Small ubiquitin-related modifier 1 (SUMO1)

Ubiquitin-like protein that can be covalently attached to proteins as a monomer or a lysine-linked polymer. Covalent attachment through an isopeptide bond to its substrates requires prior activation by the E1 complex SAE1-SAE2 and linkage to the E2 enzyme UBE2I, and can be encouraged by E3 ligases like PIAS1-4, RANBP2 or CBX4.

This post-translational modification on lysine residues of proteins plays a vital role in several of cellular processes like nuclear transport, DNA replication and repair, mitosis and signal transduction. Involved for instance in targeting RANGAP1 to the nuclear pore complex protein RANBP2.