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. Author manuscript; available in PMC: 2010 Sep 15.
Published in final edited form as: Biochemistry. 2009 Sep 15;48(36):8516–8527. doi: 10.1021/bi900912a

Figure 4. Passive dissociation of the clamp from the clamp loader versus active clamp loading onto DNA.

Figure 4

Dissociation of the clamp from the clamp loader was measured in two different experiments by adding a solution of γc-AF488, β-QSY9, and ATP to a solution of A) excess unlabeled β and ATP or B) p/t-DNA, excess unlabeled β, and ATP. Reactions in panel B contain 0 nM (gray trace), 25 nM (blue trace), 50 nM (purple trace), 100 nM (red trace), 200 nM (green trace), or 400 nM (cyan trace) p/t-DNA. Solid black lines through the gray traces containing no p/t-DNA in panels A and B are exponential fits of the data. Final concentrations were 20 nM γc-AF488, 400 nM β-QSY9, 8 μM unlabeled β, and 0.5 mM ATP in assay buffer containing 20 mM Tris·HCl pH 7.5, 50 mM NaCl, 8 mM MgCl2, and 4% glycerol.