Metallobleomycins

Li W, Zhao C, Xia C, Antholine WE and Petering DH (2001) Comparative binding properties of metallobleomycins with DNA 10-mers. Biochemistry 40 7559-7568. 

Herein we describe the application of the strategies highlighted above to the study of DNA binding metal complexes. As an example, we describe the FID analysis and H-G crystallization of metallobleomycin (Figure 1), a clinically employed antitumor agent that has served as a paradigm for the development and... 

Cu(II) bleomycin was also analyzed using the FID assay (Figure 4). In stark contrast to the others, this metalloWeomycin failed to produce an appreciable decrease in overall F and did not exhibit FID plot curvature. Notably also, Cu(II) bleomycin did not discriminate against binding to the A/T-only cassettes the A/T-only cassettes were distributed throughout the oligonucleotide rank order in contrast to the other metallobleomycins studied. These results indicated that Cu(II) bleomycin did not bind to these hairpin substrates appreciably under... 

The preceding FID analysis of several metallobleomycins verified that the DNA binding site-selectivities of Co(III) and Fe(III) bleomycin parallel each other quite closely and also correlate to the established cleavage site-selectivity of Fe(II) bleomycin + O2. Notably different, Cu(II) bleomycin did not exhibit an FID assay response under conditions used for the other metallobleomycins. This outcome was likely due to the weaker DNA binding and fast exchange of Cu(II) bleomycin relative to other metallobleomycins (48) and was no doubt exacerbated by the presence of a competitive binding fluorophore. In spite of this limitation, the FID assay is likely to contribute to the study of additional metal complex-DNA interactions in the future. 

A second question relates to mechanisms of biological interconversions of metallobleomycins. Blm and its Fe-, Cu-, and Zn-complexes are similarly cytotoxic to cells exposed under conditions that minimize extracellular cross reaction with other metal ions, implying that each can be converted into FeBlm. Yet, Cu binds to Blm with higher afifinity than does Fe, and cellular Zn may well be available for reaction with Blm. CuBlm has also been detected in urine after administration of Blm. Opposite conclusions have been reached on whether copper can be removed from Blm by reductive ligand substitution using thiol reagents. 

Solution Properties of Metallobleomycins Related to the DNA Damage Reaction... 

The early publication of the crystal structure of the metal domain of CuBlm, which lacks the disaccharide, remains the only X-ray structure of a metallob-leomycin species, and so continues to serve as a model for the metal-ligand structure of various metallobleomycins. As seen in Figure 3, its copper ion is bound to the five nitrogen atoms denoted by dots in Figure 1. 

Metallobleomycin-DNA Interactions Structures and Reactions Related to Bleomycin-Induced DNA Damage David H. Petering, Qunkai Mao, Wenbao Li,... 

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