MECHANISM OF ACTION OF ACLACINOMYCIN-A .2. INTERACTION WITH DNA AND WITH TUBULIN

Aclacinomycin A was observed to effect the thermal denaturation of DNA and to increase Tm. The visible absorption spectrum of the antibiotic showed bathochromic and hypo-chromic shifts upon reaction with native and heat-denatured DNA. [14C]Aclacinomycin A was demonstrated by equilibrium dialysis to bind to DNA. Native calf thymus DNA appeared to possess one binding site per ca. 6 nucleotides for the antibiotic with an apparent association constant of ca. 1.2×106 M–1. Heat-denatured DNA showed much less affinity for the antibiotic: one binding site per ca. 6 nucleotides with an apparent binding constant of ca. 3.5×104 M-1. The difference of association constants between double- and single-stranded DNAs suggested that the antibiotic may be intercalated between base pairs of the DNA double helix. [14C]Aclacinomycin A exhibited higher affinity for poly(dAdT) than for poly(dIdC). The antibiotic showed a significant difference spectrum with porcine tubulin, indicating an interaction with tubulin. The binding to tubulin was also demonstrated by equilibrium dialysis of [14C]aclacinomycin A and tubulin. © 1979, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.