In vitro SUMO-1 modification requires two enzymatic steps, E1 and E2

Biochem Biophys Res Commun. 1999 Jan 27;254(3):693-8. doi: 10.1006/bbrc.1998.9995.


The SUMO-1 has been identified as a protein that is highly similar to ubiquitin and shown to conjugate to RanGAP1, PML, Sp200 and I kappa B alpha. The conjugation steps are thought to be similar to those of ubiquitination; and human Ubc9, which is homologous to the E2 enzyme for the ubiquitin conjugation step, was identified and shown to be necessary for the conjugation of SUMO-1 to its target protein. Other essential enzymes involved in this modification, however, remain to be clarified. Here we cloned human Sua1 (SUMO-1 activating enzyme) and hUba2, which are human homologs of yeast Saccharomyces cerevisiae Aos1 and Uba2, respectively. The recombinant proteins, Sua1p and hUba2p, formed a complex. In this complex, hUba2 bound SUMO-1 and this complex had the activity of the SUMO-1 activating enzyme. Furthermore, in an in vitro system, RanGAP1 was modified by SUMO-1 in the presence of Sua1p/Uba2p and hUbc9p, showing that the modification of SUMO-1 could be catalyzed by two enzyme steps, although ubiquitination usually requires three enzyme steps.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carrier Proteins / metabolism
  • Cloning, Molecular
  • GTPase-Activating Proteins*
  • HeLa Cells
  • Humans
  • Ligases / chemistry
  • Ligases / genetics
  • Ligases / metabolism
  • Molecular Sequence Data
  • Proteins / chemistry
  • Proteins / genetics
  • Proteins / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • SUMO-1 Protein
  • Sequence Homology, Amino Acid
  • Ubiquitin-Activating Enzymes*
  • Ubiquitin-Protein Ligases
  • Ubiquitins / metabolism*


  • Carrier Proteins
  • GTPase-Activating Proteins
  • Proteins
  • RANGAP1 protein, human
  • Recombinant Proteins
  • SUMO-1 Protein
  • UBA2 protein, human
  • Ubiquitins
  • Ubiquitin-Protein Ligases
  • Ligases
  • SAE1 protein, human
  • Ubiquitin-Activating Enzymes

Associated data

  • GENBANK/AF090384
  • GENBANK/AF090385