INTERACTION OF KANCHANOMYCIN WITH NUCLEIC ACIDS .I. PHYSICAL PROPERTIES OF COMPLEX

Kanchanomycin, a highly cytotoxic antibiotic, which disrupts cellular synthetic processes,including inhibition of deoxyribonucleic acid dependent ribonucleic acid and deoxyribonucleic acid polymerases, forms stable complexes with various polynucleotides. Changes in the visible absorptionspectrum of kanchanomycin indicate that the antibiotic interacts with polynucleotides only in the presence of Mg2+. An initial complex (I) forms immediately and changes with time to a second complex (II) with different spectral properties. pH titration studies suggest that Mg2+ interacts with the first dissociable group of kanchanomycin and complex II formation involves asecond dissociable group. There appears to be no base specificity or requirement for a given secondary structure in the polynucleotide for the initial complex formation. Of all the polynucleotides studied, only polyadenylic acid forms a stable initial complex, which does not convert into complex II. Both complex forms are retained on Millipore filters. Complex formation is completely inhibitedby 0.1 m NaCl. Complex I, but not complex II, can be partially dissociated by NaCl. Complex I is readily dissociated by EDTA; complex II is only slowly dissociated by EDTA. Kanchanomycin (in the second complex) decreases the buoyant density of d(A-T)n increases the sedimentation rate of d(A-T)n and increases the viscosity of deoxyribonucleic acid. Kanchanomycin does not increase the temperature of thermal transition of d(A-T)n. Although the spectral changes require a Mg2+ concentration equal to the kanchanomycin concentration, the retention of the kanchanomycin-Mg2+-polynucleotide complex on Millipore filters and the changes in viscosity of deoxyribonucleic acid require a Mg2+ concentration equal to the nucleotide concentration. © 1969, American Chemical Society. All rights reserved.