title: Insights into ubiquitin-conjugating enzyme/ co-activator interactions from the structure of the Pex4p:Pex22p complex.
abstract: Ubiquitin-conjugating enzymes (E2s) coordinate distinct types of ubiquitination via specific E3 ligases, to a large number of protein substrates. While many E2 enzymes need only the presence of an E3 ligase for substrate ubiquitination, a number of E2s require additional, non-canonical binding partners to specify their function. Here, we have determined the crystal structure and function of an E2/co-activator assembly, the Pex4p:Pex22p complex. The peroxisome-associated E2 enzyme Pex4p binds the peroxisomal membrane protein Pex22p through a binding site that does not overlap with any other known interaction interface in E2 enzymes. Pex22p association enhances Pex4p's ability to transfer ubiquitin to a substrate in vitro, and Pex22p binding-deficient forms of Pex4p are unable to ubiquitinate the peroxisomal import receptor Pex5p in vivo. Our data demonstrate that the Pex4p:Pex22p assembly, and not Pex4p alone, functions as the E2 enzyme required for Pex5p ubiquitination, establishing a novel mechanism of E2 enzyme regulation.
authors.affiliation: Structural Biology Unit, European Molecular Biology Laboratory, Hamburg, Germany. c.williams@embl-hamburg.de
authors.forename: Chris
authors.initials: C
authors.lastname: Williams
authors.forename: Marlene
authors.initials: M
authors.lastname: van den Berg
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.forename: Will A
authors.initials: WA
authors.lastname: Stanley
authors.forename: Ben
authors.initials: B
authors.lastname: Distel
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilmanns
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D010446:Peptide Fragments / Q000378:metabolism; D000074401:Peroxins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009097:Multienzyme Complexes; C076587:PEX4 protein, S cerevisiae; C499509:PEX5 protein, S cerevisiae; D010446:Peptide Fragments; D000074401:Peroxins; D000074435:Peroxisome-Targeting Signal 1 Receptor; C539583:Pex22 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin
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