Abstract

We have studied the light-activated cleavage of DNA by cobalt-bleomycin using a series of synthetic DNA fragments containing (AT)n and (GC)n. This cleavage reaction requires high concentrations of the antibiotic and appears to be a stoichiometric process rather than a catalytic process. We find that, in common with the iron-complex, cobalt-bleomycin can cleave at ApT steps within regions of alternating AT residues; ApT steps within other sequences including (AAT)n. (ATP)n are not good substrates for cobalt-bleomycin cleavage. Some repetitive regions display an alternating pattern of cleavage products, revealing the preferred arrangement of ligand molecules along a saturated DNA lattice. A similar repetitive pattern is found for diethylpyrocarbonate modification and hydroxyl-radical cleavage. Although cleavage of ApT and GpC proceeds at equivalent rates, the data suggest that bleomycin binds more tightly to the latter. Adenine residues on the 3' side of both GpC-cleavage and ApT-cleavage sites are rendered more reactive to diethylpyrocarbonate, consistent with a ligand-induced alteration in local DNA structure. The cobalt-bleomycin-binding site consists of not more than four base pairs, and may be as small as three base pairs.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.