Search

Bleomycins are a group of glycopeptide antibiotics synthesized by Streptomyces verticillus that are widely used for the treatment of various neoplastic diseases. These antibiotics have the ability to chelate a metal center, mainly Fe(II), and cause site-specific DNA cleavage. Bleomycins are differentiated by their C-terminal regions. Although this antibiotic family is a successful course of treatment for some types of cancers, it is known to cause pulmonary fibrosis. Previous studies have identified that bleomycin-related pulmonary toxicity is linked to the C-terminal region of these drugs. This region has been shown to closely interact with DNA. We examined the binding of Zn(II)peplomycin and Zn(II)bleomycin-A 2 to a DNA hairpin of sequence 5'-CCAGTATTTTTACTGG-3', containing the binding site 5'-GT-3', and compared the results with those obtained from our studies of the same MBLMs bound to a DNA hairpin containing the binding site 5'-GC-3'. We provide evidence that the DNA base sequence has a strong impact in the final structure of the drug-target complex.

The antibiotics known as bleomycins constitute a family of natural products clinically employed for the treatment of a wide spectrum of cancers. The drug acts as an antitumor agent by virtue of the ability of a metal complex of the antibiotic to cleave DNA. Bleomycins are differentiated by their C-terminal regions. Previous structural studies involving metal-bleomycin-DNA triads have allowed the identification of the bithiazole-(C-terminus substituent) segment in this molecule as the one that most closely interacts with DNA. Three different modes of binding of metallo-bleomycins to DNA (partial or total intercalation of the bithiazole unit between DNA bases, or binding to the minor groove) have been proposed in the literature. The therapeutic use of bleomycin is frequently associated with the development of pulmonary fibrosis. The severity of this side effect has been attributed to the C-terminus of the antibiotic by some researchers. The degree of pulmonary toxicity of bleomycin-A 2 and -A 5 , were found to be higher than those of bleomycin-B 2 and peplomycin. Since the introduction of Blenoxane to clinical medicine in 1972, attempts have been made at modifying the basic bleomycin structure at the C-terminus to improve its therapeutic index. However, the pharmacological and toxicological importance of particular C-termini on bleomycin remains unclear. The present study was designed to determine the effect of Zn(II)bleomycin-A 2 , -A 5 , -B 2 , and Zn(II)peplomycin on the structure of a DNA hairpin containing the 5'-GC-3' binding site. We provide evidence that different Zn(II)bleomycins affect the structure of the tested DNA segment in different fashions.