• Register
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.


Leaving Community

Are you sure you want to leave this community? Leaving the community will revoke any permissions you have been granted in this community.


Characterization of two polyubiquitin binding sites in the 26 S protease subunit 5a.

Ubiquitylated proteins are degraded by the 26 S protease, an enzyme complex that contains 30 or more unique subunits. One of these proteins, subunit 5a (S5a), has been shown to bind ubiquitin-lysozyme conjugates and free polyubiquitin chains. Using deletional analysis, we have identified in the carboxyl-terminal half of human S5a, two independent polyubiquitin binding sites whose sequences are highly conserved among higher eukaryotic S5a homologs. The sites are approximately 30-amino acids long and are separated by 50 intervening residues. When expressed as small fragments or when present in full-length S5a molecules, the sites differ at least 10-fold in their apparent affinity for polyubiquitin chains. Each binding site contains 5 hydrophobic residues that form an alternating pattern of large and small side chains, e.g. Leu-Ala-Leu-Ala-Leu, and this pattern is essential for binding ubiquitin chains. Based on the importance of the alternating hydrophobic residues in the binding sites and previous studies showing that a hydrophobic patch on the surface of ubiquitin is essential for proteolytic targeting, we propose a model for molecular recognition of polyubiquitin chains by S5a.

Pubmed ID: 9488668


  • Young P
  • Deveraux Q
  • Beal RE
  • Pickart CM
  • Rechsteiner M


The Journal of biological chemistry

Publication Data

March 6, 1998

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK46984
  • Agency: NIGMS NIH HHS, Id: GM37009

Mesh Terms

  • Amino Acid Sequence
  • Binding Sites
  • Biopolymers
  • Conserved Sequence
  • Humans
  • Molecular Sequence Data
  • Muramidase
  • Mutagenesis, Site-Directed
  • Peptide Fragments
  • Peptide Hydrolases
  • Polyubiquitin
  • Proteasome Endopeptidase Complex
  • Protein Binding
  • Recombinant Proteins
  • Sequence Deletion
  • Sequence Homology, Amino Acid
  • Ubiquitins