Small ubiquitin-like modifier protein that post-translationally regulates protein stability, localization, and transcriptional activity via SUMOylation. Recombinant human SUMO1 (UBL1) (2-97) was expressed in E. coli cells using an N-terminal His tag. Molecular Weight ~19kDa. Supplied as sterile 50 mM sodium phosphate, pH 7.5, 300mM NaCl, 50-200mM imidazole, 0-0.1mM PMSF, 0.2-1.0mM DTT, 10-25% glycerol. For optimal storage, aliquot target into smaller quantities. Avoid repeated handling and multiple freeze/thaw cycles.