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International Conference on Complex Systems (ICCS2006)

Salt Dependent Binding of T7 Gene 2.5 Protein to DNA from Single Molecule Force Spectroscopy

Leila Shokri
Department of Physics, Northeastern University

Boriana Marintcheva
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School

Charles C. Richardson
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School

Mark C. Williams
Department of Physics, Northeastern University

     Full text: Not available
     Last modified: March 30, 2006

The gene 2.5 protein (gp2.5) of bacteriophage T7 binds preferentially to single-stranded DNA (ssDNA). This property is essential for its role in DNA replication, recombination, and repair. In this work the interactions between single DNA molecules and gp2.5 and its deletion mutant lacking 26 C-terminal amino acids, gp2.5-delta26C, are investigated using single molecule stretching, and the effects of these proteins on the mechanical stability of DNA molecules are quantitatively analyzed using a model of DNA force-induced melting. We show for the first time that gp2.5 is capable of slowly destabilizing natural dsDNA. We measured the helix-coil transition free energy, binding site size and the association constant of these proteins to ssDNA over a range of salt and protein concentrations. The results are used to characterize the electrostatic and non-electrostatic interactions that determine the DNA-protein binding in each case.

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