Sequence-specific Recognition of DNA. Nuclear Magnetic Resonance Assignments and Structural Comparison of Wild-type and Mutant Lambda OR3 Operator DNA

The resonances of all the base protons and most of the sugar protons in both strands of the 17 base-pair OR3 operator of the phage lambda, and of the vC3 single base-pair mutant, have been assigned using two-dimensional nuclear magnetic resonance methods. The chemical shift and nuclear Overhauser effect data for these two DNA sequences reveal no structural perturbation at sites distal to the mutation, neither are there significant changes in structure immediately surrounding the altered base-pair in the mutant sequence. These results are consistent with the model proposed by Ohlendorf et al. (1982), based on crystallographic data on the cro protein, for the OR3-cro protein interaction. The data from these solution studies are examined and discussed in the light of this model. This work demonstrates that nuclear magnetic resonance chemical shifts and nuclear Overhauser effect intensities provide a method for comparing the solution structures of DNA molecules. From the resolution available in the spectra of the 17 base-pair operators studied, it is clear that DNA duplexes of up to 30 or more base-pairs can be studied using phase-sensitive methods.