Interaction of mutagenic tryptophan pyrolysate with DNA: CD spectral study on the binding specificity

Abstract

The interactions of DNA duplexes with 3-amino 1,4-dimethyl-5H-pyrido[4,3-b]indole(Trp-P-1), a potent mutacarcinogen isolated from tryptophan pyrolysate, have been studied using CD spectroscopy. The results are that (a) the spectral change of B-form DNA caused by the interaction with Trp-P-1 is biphasic, i.e. the enlargement of CD bands characteristic to the B-DNA conformation in the range of r ([Trp-P-1]/[DNA]) = 0–2.5, followed by the rapid transition to the non-B conformation at r > 2.5; (b) this transition degree of B to non-B conformation of DNA is not necessarily dependent on the G-C content; and (c) the salt-induced Z-DNA is transformed to B-DNA (0 < r < 0.1) and then to non-B-DNA (r > 5), depending on the concentration of Trp-P-1 added. These data indicate that the non-covalent interaction of Trp-P-1 with DNA is mainly dependent on the B-DNA conformation.