The recently discovered small ubiquitin-related modifier SUMO-1 belongs to the growing family of ubiquitin-related proteins involved in postranslational protein modification. Unlike ubiquitin, SUMO-1 does not appear to target proteins for degradation but seems to be involved in the modulation of protein-protein interactions ...
The recently discovered small ubiquitin-related modifier SUMO-1 belongs to the growing family of ubiquitin-related proteins involved in postranslational protein modification. Unlike ubiquitin, SUMO-1 does not appear to target proteins for degradation but seems to be involved in the modulation of protein-protein interactions. Independent studies demonstrate an essential function of SUMO-1 in the regulation of nucleo-cytoplasmic transport, and suggest a role in cell-cycle regulation and apoptosis. Here, we present the first three-dimensional structure of SUMO-1 solved by NMR. Although having only 18% amino acid sequence identity with ubiquitin, the overall structure closely resembles that of ubiquitin, featuring the betabetaalphabetabetaalphabeta fold of the ubiquitin protein family. In addition, the position of the two C-terminal Gly residues required for isopeptide bond formation is conserved between ubiquitin and SUMO-1. The most prominent feature of SUMO-1 is a long and highly flexible N terminus, which protrudes from the core of the protein and which is absent in ubiquitin. Furthermore, ubiquitin Lys48, required to generate ubiquitin polymers, is substituted in SUMO-1 by Gln69 at the same position, which provides an explanation of why SUMO-1 has not been observed to form polymers. Moreover, the hydrophobic core of SUMO-1 and ubiquitin is maintained by conserved hydrophobic residues, whereas the overall charge topology of SUMO-1 and ubiquitin differs significantly, suggesting specific modifying enzymes and target proteins for both proteins.
Related Citations:
A Small Ubiquitin-Related Polypeptide Involved in Targeting Rangap1 to Nuclear Pore Complex Protein Ranbp2 Mahajan, R., Delphin, C., Guan, T., Gerace, L., Melchior, F. (1997) Cell 88: 97
Preferential Modification of Nuclear Proteins by a Novel Ubiquitin-Like Molecule Kamitani, T., Nguyen, H.P., Yeh, E.T. (1997) J Biol Chem 272: 14001
A Novel Ubiquitin-Like Modification Modulates the Partitioning of the Ran-Gtpase-Activating Protein Rangap1 between the Cytosol and the Nuclear Pore Complex Matunis, M.J., Coutavas, E., Blobel, G. (1996) J Cell Biol 135: 1457
Organizational Affiliation:
Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany.
Download Mendeley
