In vitro SUMO-1 modification requires two enzymatic steps, E1 and E2.
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.
Mesh Terms:
Amino Acid Sequence, Carrier Proteins, Cloning, Molecular, GTPase-Activating Proteins, Hela Cells, Humans, Ligases, Molecular Sequence Data, Proteins, Recombinant Proteins, SUMO-1 Protein, Sequence Homology, Amino Acid, Ubiquitin-Activating Enzymes, Ubiquitin-Protein Ligases, Ubiquitins
Amino Acid Sequence, Carrier Proteins, Cloning, Molecular, GTPase-Activating Proteins, Hela Cells, Humans, Ligases, Molecular Sequence Data, Proteins, Recombinant Proteins, SUMO-1 Protein, Sequence Homology, Amino Acid, Ubiquitin-Activating Enzymes, Ubiquitin-Protein Ligases, Ubiquitins
Biochem. Biophys. Res. Commun.
Date: Jan. 27, 1999
PubMed ID: 9920803
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