Elements of a DNA-polypeptide recognition code: electrostatic potential around the double helix, and a stereospecific model for purine recognition.

A model for stereospecific complex between a polynucleotide double helix and a twisted beta-ribbon type polypeptide is described. The beta ribbon lies in the major groove with alternate side chains pointing toward the interior of the groove. The base-amino acid complementarities are: Arg, G and Asn or Gln, A. It is shown that this complex can: (a) distinguish between G and A in homopolar sequences; (b) the complex is stabilized by approx. 6 Kcal/mole per hydrogen bond per base pair; (c) the required backbone conformation is in the permitted range of Ramachandran plots.