PMID:12445774
| Citation |
Wah, DA, Levchenko, I, Baker, TA and Sauer, RT (2002) Characterization of a specificity factor for an AAA+ ATPase: assembly of SspB dimers with ssrA-tagged proteins and the ClpX hexamer. Chem. Biol. 9:1237-45 |
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| Abstract |
SspB, a specificity factor for the ATP-dependent ClpXP protease, stimulates proteolysis of protein substrates bearing the ssrA degradation tag. The SspB protein is shown here to form a stable homodimer with two independent binding sites for ssrA-tagged proteins or peptides. SspB by itself binds to ClpX and stimulates the ATPase activity of this enzyme. In the presence of ATPgammaS, a ternary complex of SspB, GFP-ssrA, and the ClpX ATPase was sufficiently stable to isolate by gel-filtration or ion-exchange chromatography. This complex consists of one SspB dimer, two molecules of GFP-ssrA, and one ClpX hexamer. SspB dimers do not commit bound substrates to ClpXP degradation but increase the affinity and cooperativity of binding of ssrA-tagged substrates to ClpX, facilitating enhanced degradation at low substrate concentrations. |
| Links | |
| Keywords |
Adenosine Triphosphatases/metabolism; Carrier Proteins/metabolism; Cleavage And Polyadenylation Specificity Factor/metabolism; Dimerization; Endopeptidase Clp; Escherichia coli Proteins/metabolism; Green Fluorescent Proteins; Luminescent Proteins; Molecular Chaperones; Protein Binding; Proteins/metabolism; Serine Endopeptidases/metabolism |
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