INTERACTION WITH DNA OF A SYNTHETIC PEPTIDE-CONTAINING A PART OF THE DNA-BINDING DOMAIN OF TRANSCRIPTION ACTIVATOR V-JUN

Synthesis and interaction with DNA are described for a 26-residue pept ide containing two copies of a fragment of the DNA-binding domain of t he transcription activator v-Jun. The CD spectroscopy data showed the synthetic peptide to be in a random conformation in an aqueous solutio n, and partially in alpha-helical conformation in the presence of 20% trifluoroethanol. In 40% trifluoroethanol the relative content of alph a-helix increases to about 80%. The peptide was shown to form two type s of complex with DNA. The first is saturated at one peptide molecule per six base pairs. With a further increase of the peptide/DNA molar r atio the binding becomes a cooperative process. The second complex is saturated at one peptide molecule per four DNA base pairs. The associa tion constant for the first type of complex in the presence of 0.2 M N aCl was estimated at 1.10(-5) M(-1). The peptide binds more strongly t o poly(dG).poly(dC) and poly(dA).poly(dT) than to poly[d(GC)].poly[d(G C)]. We found that the DNA minor groove-binding antibiotic distamycin A competes effectively with the peptide for the binding to poly(dA) po ly(dT).