Abstract Protein-nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein-DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH<inf>3</inf> <sup>+</sup> groups forming the intermolecular ion pairs. A characteristic change in their <sup>1</sup>H and <sup>15</sup>N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain <sup>15</sup>N and DNA phosphorodithiaote <sup>31</sup>P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein-RNA complexes as well.
- Hydrogen bonds
- Ion pairs
- NH<inf>3</inf><sup>+</sup> groups
- Protein side chains
- Protein-nucleic acid interactions
ASJC Scopus subject areas