title: Zn2+-induced reversible dissociation of subunit Rpn10/p54 of the Drosophila 26 S proteasome.
abstract: In the presence of Zn2+, the Drosophila 26 S proteasome disassembles into RP (regulatory particle) and CP (catalytic particle), this process being accompanied by the dissociation of subunit Rpn10/p54, the ubiquitin receptor subunit of the proteasome. The dissociation of Rpn10/p54 induces extensive rearrangements within the lid subcomplex of the RP, while the structure of the ATPase ring of the base subcomplex seems to be maintained. As a consequence of the dissociation of the RP, the peptidase activity of the 26 S proteasome is lost. The Zn2+-induced structural and functional changes are fully reversible; removal of Zn2+ is followed by reassociation of subunit Rpn10/p54 to the RP, reassembly of the 26 S proteasome and resumption of the peptidase activity. After the Zn2+-induced dissociation, Rpn10/p54 interacts with a set of non-proteasomal proteins. Hsp82 (heat-shock protein 82) has been identified by MS as the main Rpn10/p54-interacting protein, suggesting its role in the reassembly of the 26 S proteasome after Zn2+ removal. The physiological relevance of another Rpn10/p54-interacting protein, the Smt3 SUMO (small ubiquitin-related modifier-1)-activating enzyme, detected by chemical cross-linking, has been confirmed by yeast two-hybrid analysis. Besides the Smt3 SUMO-activating enzyme, the Ubc9 SUMO-conjugating enzyme also exhibited in vivo interaction with the 5'-half of Rpn10/p54 in yeast cells. The mechanism of 26 S proteasome disassembly after ATP depletion is clearly different from that induced by Zn2+. Rpn10/p54 is permanently RP-bound during the ATP-dependent assembly-disassembly cycle, but during the Zn2+ cycle it reversibly shuttles between the RP-bound and free states.
authors.affiliation: Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, P.O. Box 521, Hungary.
authors.forename: Petra
authors.initials: P
authors.lastname: Kiss
authors.forename: Aron
authors.initials: A
authors.lastname: Szabó
authors.forename: Eva
authors.initials: E
authors.lastname: Hunyadi-Gulyás
authors.forename: Katalin F
authors.initials: KF
authors.lastname: Medzihradszky
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Lipinszki
authors.forename: Margit
authors.initials: M
authors.lastname: Pál
authors.forename: Andor
authors.initials: A
authors.lastname: Udvardy
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004330:Drosophila / Q000201:enzymology*; D006360:Heat-Shock Proteins / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
chemical_list: D006360:Heat-Shock Proteins; D021122:Protein Subunits; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D015032:Zinc