SUMO1 activating enzyme subunit 1(SAE1) Homo sapiens Posttranslational modification of proteins by the addition of the small protein SUMO (see SUMO1, MIM 601912), or sumoylation, regulates protein structure and intracellular localization. SAE1 and UBA2 (MIM 613295) form a heterodimer that functions as a SUMO-activating enzyme for the sumoylation of proteins (Okuma et al., 1999 [PubMed 9920803]).[supplied by OMIM, Mar 2010],function:The dimeric enzyme acts as a E1 ligase for SUMO1, SUMO2, SUMO3, and probably SUMO4. It mediates ATP-dependent activation of SUMO proteins and formation of a thioester with a conserved cysteine residue on SAE2.,pathway:Protein modification, protein sumoylation.,PTM:Phosphorylated upon DNA damage, probably by ATM or ATR.,similarity:Belongs to the ubiquitin-activating E1 family.,subunit:Heterodimer of SAE1 and SAE2. The complex binds SUMO proteins via SAE2.,tissue specificity:Expression level increases during S phase and drops in G2 phase (at protein level).,