Polyarginine and polylysine bind to polyaspartate and polyglutamate forming electrostatically neutral stoichiometric complexes. Arginine binds glutamate and aspartate at least 100-fold more strongly than lysine. Arginine forms two hydrogen bonds with the oppositely charged amino acids, while lysine forms only one. The positive charges should not be considered entirely equivalent in proteins if carried by lysine or arginine.
The authors declare no competing financial interest.