title: Binding and degradation of heterodimeric substrates by ClpAP and ClpXP.
abstract: ClpA and ClpX function both as molecular chaperones and as the regulatory components of ClpAP and ClpXP proteases, respectively. ClpA and ClpX bind substrate proteins through specific recognition signals, catalyze ATP-dependent protein unfolding of the substrate, and when in complexes with ClpP translocate the unfolded polypeptide into the cavity of the ClpP peptidase for degradation. To examine the mechanism of interaction of ClpAP with dimeric substrates, single round binding and degradation experiments were performed, revealing that ClpAP degraded both subunits of a RepA homodimer in one cycle of binding. Furthermore, ClpAP was able to degrade both protomers of a RepA heterodimer in which only one subunit contained the ClpA recognition signal. In contrast, ClpXP degraded both subunits of a dimeric substrate only when both protomers contained a recognition signal. These data suggest that ClpAP and ClpXP may recognize and bind substrates in significantly different ways.
authors.affiliation: Laboratory of Molecular Biology, NCI, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Suveena
authors.initials: S
authors.lastname: Sharma
authors.forename: Joel R
authors.initials: JR
authors.lastname: Hoskins
authors.forename: Sue
authors.initials: S
authors.lastname: Wickner
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D049071:Endopeptidase Clp / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000378:metabolism; D012313:RNA / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D021122:Protein Subunits; D015534:Trans-Activators; C045264:replication initiator protein; D012313:RNA; C483568:ClpA protease, E coli; C483572:ClpP protease, E coli; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities; D004265:DNA Helicases