Produced in E. coli. Human SUMO-1 is fused to a His-tag.
SUMO (small ubiquitin-related modifier) is a member of a family of ubiquitin-like proteins involved in the regulation of the cellular functions of a wide variety of proteins. Four members of the SUMO family have been described in vertebrates, SUMO-1 and the close homologues SUMO-2 and SUMO-3, with some 50% homology between SUMO-1 and SUMO-2/3. Although a fourth SUMO (SUMO-4) has been reported, there remains considerable debate as to whether this is a real and expressed gene product.
The mechanism for SUMO conjugation is analogous to that of the ubiquitin system, relying upon utilisation of E1, E2 and (potentially) E3 cascade enzymes to covalently link the carboxy-terminal of SUMO proteins to specific lysine residues on target proteins via isopeptide bonds. Unlike ubiquitinylation, which leads, inter alia, to a degradative pathway, SUMO modification of target proteins is involved in nuclear protein targeting, formation of sub-nuclear complexes, regulation of transcriptional activities, and control of protein stability. A short sequence containing the consensus psi-K-X-D/E (where lysine is the modified amino acid, psi is a large hydrophobic residue and X is any amino acid residue) is thought to be necessary for protein SUMOylation to occur, however, SUMOylation has also been observed in cases where the consensus site is not conserved.
