Actinomycin Binding to DNA: Inability of a DNA Containing Guanine To Bind Actinomycin D

Polydeoxy (adenylyl-thymidylyl-cytidylyl) ⋅ polydeoxy(guanylyl-adenylyl-thymidylyl), a double-stranded DNA polmer of high molecular weight containing 33 percent guanine plus cytosine, binds little or no actinomycin D, as measured by five different techniques. In contrast, the sequence isomer of this DNA, polydeoxy(thymidylyl-adenylyl-cytidylyl) ⋅ polydeoxy(guanylyl-thymidylyl-adenylyl), does bind the antibiotic. Thus, the presence of guanine in a DNA is not a sufficient requisite for the binding of actinomycin D.