title: Dimerization of the human E3 ligase CHIP via a coiled-coil domain is essential for its activity.
abstract: The Hsp70-interacting E3-ubiquitin ligase CHIP has been implicated in the decision as to whether a target protein enters the refolding or the degradation pathway. To further characterize the activity of CHIP we purified untagged Homo sapiens and Drosophila melanogaster CHIP (hCHIP, dCHIP). In contrast to other E3-ubiquitin ligases, both hCHIP and dCHIP proteins formed homodimers at physiological concentrations. We identified a predicted coiled-coil region in a mixed charge segment of the hCHIP and dCHIP sequence and found it to be necessary and sufficient for dimer formation. A mutant of hCHIP lacking this segment (hCHIPdelta-(128-229)) was incapable of dimer formation, but the segment by itself (hCHIP-(128-229)) readily dimerized. Furthermore, we demonstrated that dimerization is a prerequisite for activity of hCHIP in the reconstituted ubiquitination assay. Control of dimerization may thus provide a mechanism for regulation of CHIP activity.
authors: Zentrum für Molekulare Biologie Heidelberg, Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
authors: Rainer
authors: R
authors: Nikolay
authors: Thomas
authors: T
authors: Wiederkehr
authors: Wolfgang
authors: W
authors: Rist
authors: Günter
authors: G
authors: Kramer
authors: Matthias P
authors: MP
authors: Mayer
authors: Bernd
authors: B
authors: Bukau
mesh_terms: D000818:Animals; D019281:Dimerization; D004331:Drosophila melanogaster; D004789:Enzyme Activation; D006801:Humans; D013329:Structure-Activity Relationship; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D044767:Ubiquitin-Protein Ligases