title: The N-terminal zinc binding domain of ClpX is a dimerization domain that modulates the chaperone function.
abstract: Clp ATPases are unique chaperones that promote protein unfolding and subsequent degradation by proteases. The mechanism by which this occurs is poorly understood. Here we demonstrate that the N-terminal domain of ClpX is a C4-type zinc binding domain (ZBD) involved in substrate recognition. ZBD forms a very stable dimer that is essential for promoting the degradation of some typical ClpXP substrates such as lambdaO and MuA but not GFP-SsrA. Furthermore, experiments indicate that ZBD contains a primary binding site for the lambdaO substrate and for the cofactor SspB. Removal of ZBD from the ClpX sequence renders the ATPase activity of ClpX largely insensitive to the presence of ClpP, substrates, or the SspB cofactor. All these results indicate that ZBD plays an important role in the ClpX mechanism of function and that ATP binding and/or hydrolysis drives a conformational change in ClpX involving ZBD.
authors.affiliation: Department of Biochemistry, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Urszula A
authors.initials: UA
authors.lastname: Wojtyra
authors.forename: Guillaume
authors.initials: G
authors.lastname: Thibault
authors.forename: Ashleigh
authors.initials: A
authors.lastname: Tuite
authors.forename: Walid A
authors.initials: WA
authors.lastname: Houry
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D019281:Dimerization; D049071:Endopeptidase Clp; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones / Q000502:physiology*; D016296:Mutagenesis; D015032:Zinc / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities; D015032:Zinc