DNA-protein interactions play important roles in a number of key biological processes, yet these are not fully understood.  Here, we report a systematic, predictable approach to control these interactions at constant pH, ionic strength and temperature. To demonstrate the versatility of the approach, we chose a non-DNA binding protein, glucose oxidase (GO, acidic protein with an isoelectric point of 5.5), and we chemically modified its carboxyl groups with increasing numbers of triethylenetetraamine (TETA) by carbodiimide chemistry. Conjugation of TETA to GO produced positively charged GO-TETA analogs whose net charge was controlled by controlling the extent of chemical conjugation with TETA.  While GO has no affinity for the negatively charged DNA double helix, the GO-TETA conjugates indicated high affinities, in the range of 2.1 x 107M-1.  Thus, the DNA-binding affinities of a protein can be controlled by benign modification of its surface carboxyl groups. Binding is entirely entropy driven with an enthalpic penalty of 30.4 kcal/mol and intrinsic propensity (?G) of -9.8 kcal/mol.  The DNA-bound GO-TETA is highly enzymatically active. One exciting observation, in addition, was that a minimum of + 27 charge is required for binding to DNA, and the affinity suddenly jumped to very high values above this charge, and it was nearly zero below this. This is the very first example of an artificial DNA-binding enzyme, and it provided a rational, predictable tool to control enzyme-DNA interactions at the molecular level.

Chemical control of protein-DNA interactions: Step-binding of modified glucose oxidase to double helical DNA

247th National Meeting (2014)

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