The binding of the antitumor antibiotic chartreusin to poly(dA-dT).poly(dA-dT), poly(dG-dC).poly(dG-dC), calf thymus DNA, transfer RNA, and ribosomal RNA.

Chartreusin binds cooperatively to poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC). Both the site-exclusion model and the specific site model yield cooperative binding constants of about 5 X 10(5) M-1 and 3 X 10(5) M-1 for the AT and GC polymers, respectively, and the same stoichiometry and intrinsic binding constant for both polymers of 5 nucleotides per binding site and 3.1 X 10(4) M-1. The Scatchard plot for calf thymus DNA is curved in the opposite sense from that of cooperative binding. These binding data did not fit the site-exclusion model with the cooperative binding parameter as a variable nor the specific site, negative-cooperative binding model. The site-exclusion model with a cooperative binding parameter of unity yielded a binding constant of about 4 X 10(4) M-1 and a stoichiometry of about 5 nucleotides per binding site. The same model for transfer and ribosomal RNA yielded binding constants of 5 X 10(3) M-1 and 7 X 10(3) M-1 and stoichiometries of about 13 and 6 nucleotides per binding site, respectively.