A SYNTHETIC ZINC-CHELATING PEPTIDE COMPETES WITH ANTIBIOTICS FOR BINDING-SITES IN THE DNA MINOR-GROOVE

The effect of sibiromycin, distamycin, and its analogs on binding with DNA and poly(dA). poly(dT) of a 23-residue synthetic zinc-binding pep tide - a part of the yeast transcriptional activator GAL4 DNA-binding domain - has been studied. Fluorimetry and circular dichroism data hav e shown that the synthetic peptide competes with distamycin A analogs for the binding sites on DNA. Sibiromycin, which forms a covalent bond with a guanine 2-amino group in the DNA minor groove, displaces the p eptide from the complex with a 19-bp self-complementary oligonucleotid e, a specific target for GAL4. The peptide can bind with glucosylated phage T2 DNA, though its affinity to T2 DNA is lower than to calf thym us DNA under the same conditions. A method based on binding isotherms for the distamycin A analog on poly(dA). poly(dT) in the presence and in the absence of the peptide is proposed, allowing one to estimate th e binding constants and sizes of the binding sites for the synthetic p eptide on poly(dA). poly(dT). Using the isotherms of binding on poly(d A). poly(dT) for two distamycin analogs with binding constants differi ng about 60 times, the peptide binding constant in the presence of 0.1 M NaCl was estimated at (1.4-1.8). 10(7) M(-1).