Recombinant Human SUMO E1 (SAE1/UBA2) Protein, CF

Small Ubiquitin-like Modifier (SUMO) Activating Enzyme Subunit 1 (SAE1) is the highly conserved human ortholog of yeast Ubiquitin-activating enzyme E1-like (UBA2) (1). These SUMO-activating (E1) enzymes are critical for the enzymatic attachment of SUMO molecules to a target protein by a post-translational modification process termed SUMOylation (2-4).  The ATP-dependent E1 enzyme charges the SUMO by forming a high-energy thiol ester intermediate which is transferred to the UBE2I/Ubc9 SUMO-conjugating (E2) enzyme (5,6). The second step is the trans-esterification reaction whereby SUMO is transferred to Cys⁹³ of UbcH9. UBE2I/Ubc9 is the only known E2 that is able to mediate the conjugation of SUMO to lysine residues on a variety of cellular targets, usually in the absence of a Ubiquitin ligase (E3). Although UBE2I/Ubc9 can directly recognize and modify lysine residues contained in a SUMOylation motif, E3-like factors most likely facilitate the SUMOylation of specific substrates.

Conjugation of the ubiquitin-like modifier SUMO (Sentrin) requires the activities of the heterodimeric E1 (SAE1/UBA2) and the UbcH9 E2 enzyme. The dimeric activating enzyme utilizes ATP to adenylate the C-terminal glycine residue of all SUMO proteins, forming a high energy thiolester bond with the cysteine residue of UBA2 and the concomitant release of AMP and PPi. The second step is the trans-esterification reaction whereby SUMO is transferred to Cys⁹³ of UbcH9.