Crystal structure of murine/human Ubc9 provides insight into the variability of the ubiquitin-conjugating system

J Biol Chem. 1997 Aug 22;272(34):21381-7. doi: 10.1074/jbc.272.34.21381.


Murine/human ubiquitin-conjugating enzyme Ubc9 is a functional homolog of Saccharomyces cerevisiae Ubc9 that is essential for the viability of yeast cells with a specific role in the G2-M transition of the cell cycle. The structure of recombinant mammalian Ubc9 has been determined from two crystal forms at 2.0 A resolution. Like Arabidopsis thaliana Ubc1 and S. cerevisiae Ubc4, murine/human Ubc9 was crystallized as a monomer, suggesting that previously reported hetero- and homo-interactions among Ubcs may be relatively weak or indirect. Compared with the known crystal structures of Ubc1 and Ubc4, which regulate different cellular processes, Ubc9 has a 5-residue insertion that forms a very exposed tight beta-hairpin and a 2-residue insertion that forms a bulge in a loop close to the active site. Mammalian Ubc9 also possesses a distinct electrostatic potential distribution that may provide possible clues to its remarkable ability to interact with other proteins. The 2-residue insertion and other sequence and structural heterogeneity observed at the catalytic site suggest that different Ubcs may utilize catalytic mechanisms of varying efficiency and substrate specificity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis Proteins*
  • Binding Sites
  • Consensus Sequence
  • Crystallography, X-Ray
  • Fungal Proteins / ultrastructure
  • Humans
  • Ligases / ultrastructure*
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Plant Proteins / ultrastructure
  • Protein Structure, Tertiary
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins*
  • Ubiquitin-Conjugating Enzymes*
  • Ubiquitins / metabolism


  • Arabidopsis Proteins
  • Fungal Proteins
  • Plant Proteins
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Ubiquitins
  • UBC1 protein, Arabidopsis
  • UBC1 protein, S cerevisiae
  • Ubiquitin-Conjugating Enzymes
  • ubiquitin-conjugating enzyme UBC4
  • Ligases
  • ubiquitin-conjugating enzyme UBC9