Minor groove to major groove an unusual DNA sequence dependent change in bend directionality by a distamycin dimer

摘要

DNA sequence dependent conformational changes induced by the minor groove binder, distamycin, have been evaluated by polyacrylamide gel electrophoresis. The distamycin binding affinity, cooperativity and stoichiometry with three target DNA sequences that have different sizes of alternating AT sites, ATAT, ATATA and ATATAT, have been determined by mass spectrometry and surface plasmon resonance to help explain the conformational changes. The results show that distamycin binds strongly to and bends five or six AT base pair minor groove sites as a dimer with positive cooperativity, while it binds to ATAT as a weak, slightly anti-cooperative dimer. The bending direction was evaluated with an in phase A-tract reference sequence. Unlike other similar monomer minor groove binding compounds, such as netropsin, the distamycin dimer changes the directionality of the overall curvature away from the minor groove to the major groove. This distinct structural effect may enable designed distamycin derivatives to have selective therapeutic effects.