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SUMO (Small Ubiquitin-like Modifier)

Like ubiquitin, the SUMO proteins are protein modifiers that are covalently attached to the epsilon-amino groups of lysine residues within substrates and play an important role in a wide variety of biological processes. The mammalian SUMO family includes at least three members, SUMO-1, SUMO-2 and SUMO-3, and SUMO-4, although the role of the latter remains poorly understood. All members are expressed in precursor form and have to be C-terminally processed to give the functionally active mature forms. In contrast to ubiquitinylation, SUMO conjugation is highly specific in terms of target lysine residues, but many aspects of substrate and lysine selection by the SUMO conjugating machinery still await clarification. SUMOylation events usually occur at a consensus motif, although not all such motifs are modified, demonstrating a need for additional specificity determinants in SUMOylation.

In other cases modification occurs at non-consensus sites. The regulation of SUMOylation is intimately linked to other post-translational modifications, including ubiquitinylation, phosphorylation and acetylation. While target proteins are predominantly conjugated to monomeric SUMO, all three SUMO family members are able to form chains in vitro. In cells, SUMOs have the potential to polymerise via internal consensus sites for SUMOylation that are present in both SUMO-2 and SUMO-3. SUMO chain formation is reversible; SUMO polymers are disassembled by SUMO proteases both in vitro and in vivo. However, the functional relevance of SUMO polymerisation is still unclear and much work focuses on the identity of the endogenous target proteins that are conjugated to SUMO polymers. There is a growing appreciation for the existence of cross-talk mechanisms between the SUMOylation and ubiquitinylation processes. Rather than being strictly parallel, these two systems have many points of intersection, and it is likely that the coordination of these two systems is a critical contributor to the regulation of many fundamental cellular events.

About SUMO Nomenclature

There is confusion within the scientific literature (including NCBI and UniProt protein databases) concerning the nomenclature used for SUMO-2 and SUMO-3 paralogs. Please note that Enzo Life Sciences uses the nomenclature proposed by Saitoh and Hinchey* for SUMO-2/SMT3A and SUMO-3/SMT3B and reports data accordingly.


Literature References

  • Small ubiquitin-related modifiers in chains: A.C. Vertegaal; Biochem. Soc. Trans. 35, 1422 (2007)
  • *Functional heterogeneity of small ubiquitin-related protein modifiers SUMO-1 versus SUMO-2/3: H. Saitoh, J. Hinchey; Biol. Chem. 275, 6252 (2000)

Featured Products

SUMO-Qapture-T® kit

Only commercially available kit for isolation and enrichment of SUMOylated Proteins

  • Fast, Simple, and Reliable assay
  • High Specificity, High Through-put Capacity
  • Amenable to analysis via Western blotting or proteomic methods

Western blot analysis of SUMO-Qapture enrichment of lysate- derived SUMO-1 modified proteins. Lane 1: MWM, Lane 2: Unbound lysate, Lane 3: Elution, Lane 4: Wash 1, Lane 5: Wash 2, Lane 6: Starting material.

Suggested Applications

  • Capture and isolation of SUMO-protein conjugates from specific cell/tissue lysates of interest with subsequent detection and analysis by Western blotting.
  • Identification of SUMO-modified protein substrates by proteomic analysis methods following release of free SUMOylated proteins in denatured form.
  • Selective purification/pull down of SUMOylated proteins from in vitro SUMOylation assays.

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