Binding of Analogues of the Antibiotics Distamycin A and Netropsin to Native DNA

• Published in: European journal of biochemistry Vol. 26; no. 1; pp. 81 - 89
• Main Authors: Zimmeer, Christoph, Luck, Gerhard, Thrum, Heinz, Pitra, Christian
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.1972
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1111/j.1432-1033.1972.tb01742.x

Binding effects of DNA with two distamycin A analogues containing four and five 1‐methyl‐pyrrole residues (distamycin A contains three of these residues) and with a degradation product of netropsin have been investigated by ultraviolet absorbance, melting and circular dichroism measurements. Increasing numbers of the methylpyrrole groups (3 to 5) enhance the thermal stability of the oligopeptide complex. On the other hand elimination of the basic groups of the netropsin molecule decreases the melting temperature of the oligopeptide · DNA complex enormously. The circular dichroism spectrum of DNA is also less affected by the degradation product compared to netropsin. Circular dichroism spectra of the complexes exhibit a pronounced band at the longer wavelength region and indicate an increasing chirality in the complex with increasing number of chromophores of the oligopeptides. From the results it is concluded that electrostatic attraction of the oligopeptides by interaction of the propionamidino and guanidino groups with the negative phosphate sites of DNA is important for the formation of the complex. However, non‐ionic forces, which have been discussed earlier, seem to be involved and may be attributed to the chromophore residues oriented in the helical grooves. The different binding tendency of the oligopeptides with DNA is discussed together with the biological activity of the oligopeptides.