title: Structural determinants for the binding of ubiquitin-like domains to the proteasome.
abstract: HHR23A, a protein implicated in nucleotide excision repair, belongs to a class of proteins containing both a ubiquitin-like (Ubl) domain and one or more ubiquitin-associated (UBA) domains, suggesting a role in the ubiquitin-proteasome pathway as well. The Ubl domain binds with high affinity to the second ubiquitin-interacting motif (UIM) of the S5a subunit of the proteasome. Here we present the solution structures of the HHR23A Ubl domain, the second UIM of S5a (UIM-2), and the Ubl:S5a-UIM-2 complex. The HHR23A Ubl domain is structurally similar to ubiquitin. The S5a UIM forms an alpha-helix with an unexpected hairpin loop that contributes to the binding interface with Ubl. The molecular determinants of the Ubl-proteasome interaction are revealed by analysis of the structures, chemical shift mapping, mutant binding studies and sequence conservation.
authors.affiliation: Department of Chemistry and Biochemistry, 405 Hilgard Avenue, PO Box 951569, University of California, Los Angeles, CA 90095-1569, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Mueller
authors.forename: Juli
authors.initials: J
authors.lastname: Feigon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017124:Conserved Sequence; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D011994:Recombinant Proteins; D025801:Ubiquitin; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease