Effects of base substitutions on the binding of a DNA-bending protein.
In order to investigate whether the 2-amino group of guanine, which lies in the minor groove of the B-form helix, can directly influence DNA flexibility and major groove recognition by proteins we have examined the properties of DNA molecules containing inosine and/or 2,6-diaminopurine (DAP) residues. Appropriately substituted tyrT(A93) DNA fragments were prepared by the polymerase chain reaction. Their mobility in non-denaturing gels was affected, consistent with changed anisotropic flexibility leading to increased curvature due to G-->I substitution and decreased curvature due to replacement of adenine with DAP. Band-shift assays of FIS protein binding revealed facilitated interaction with inosine-containing DNA and markedly reduced binding to DAP-containing DNA, attributable to altered bendability. DNase footprinting experiments confirmed that fewer sites would bind FIS in DAP-containing DNA at a given protein concentration, whereas higher levels of binding occurred with inosine-containing molecules. Thus base substitutions which affect the placement and presence of the purine 2-amino group in the minor groove can affect both the intrinsic curvature and the bendability of DNA.[1]References
- Effects of base substitutions on the binding of a DNA-bending protein. Bailly, C., Waring, M.J., Travers, A.A. J. Mol. Biol. (1995) [Pubmed]
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