EFFECT OF PROLINE RESIDUE IN POLYPEPTIDES ON THE INTERACTIONS BETWEENPOLYPEPTIDES AND DNA

The interaction between high molecular-weight synthetic polypeptides c ontaining proline residue and salmon DNA were studied by circular dich roism spectra (CD) in aqueous solution, H-1 NMR in D2O solution, and C -13 NMR spectra in solid state. The interactions were compared with th ose of polypeptides containing lysine residue and DNA. The complexes o f poly(Pro) and poly(Pro-co-Gly) with DNA were made by lyophilization after dialysis of the mixed solution of the corresponding solutions. T hese complexes were soluble in water and insoluble in 1 M NaCl, in con trast to the poly(Lys)-DNA complex, which was insoluble in water and s oluble in 1 M (mel dm(-3)) NaCl. The polypeptides containing proline r esidue (poly(Pro-co-X)) interacted with DNA in the solution, which dif fered from the interaction of poly(lys) with DNA. In addition, the int eractions of poly(Pro) and poly(Pro-co-Gly) with DNA differed from eac h other.