Binding and cleavage characteristics of the complexes formed between the neocarzinostatin chromophore and single site containing oligonucleotides

Sweet antibiotics - the role of glycosidic residues in antibiotic and antitumor activity and their randomization

A large number of antibiotics are glycosides. In numerous cases the glycosidic residues are crucial to their activity; sometimes, glycosylation only improves their pharmacokinetic parameters. Recent developments in molecular glycobiology have improved our understanding of aglycone vs. glycoside activities and made it possible to develop new, more active or more effective glycodrugs based on these findings - a very illustrative recent example is vancomycin. The majority of attention has been devoted to glycosidic antibiotics including their past, present, and probably future position in antimicrobial therapy. The role of the glycosidic residue in the biological activity of glycosidic antibiotics, and the attendant targeting and antibiotic selectivity mediated by glycone and aglycone in antibiotics some antitumor agents is discussed here in detail. Chemical and enzymatic modifications of aglycones in antibiotics, including their synthesis, are demonstrated on various examples, with particular emphasis on the role of specific and mutant glycosyltransferases and glycorandomization in the preparation of these compounds. The last section of this review describes and explains the interactions of the glycone moiety of the antibiotics with DNA and especially the design and structure-activity relationship of glycosidic antibiotics, including their classification based on their aglycone and glycosidic moiety. The new enzymatic methodology 'glycorandomization' enabled the preparation of glycoside libraries and opened up new ways to prepare optimized or entirely novel glycoside antibiotics.

DNA cleavage characteristics of non-protein enediyne antibiotic N1999A2

N1999A2 (NA2) is a new non-protein antitumor antibiotic that contains a stable 9-membered ring enediyne chromophore similar to a neocarzinostatin chromophore (NCS-chr). We have compared DNA cleavage reactions between NA2 and NCS-chr, and also clarified some characteristics of DNA strand scission by NA2. It was found that: (1) NA2 is considerably stable in nature, (2) the compound intercalates into base pairs of a DNA minor groove and decreases its base-attacking frequency in the order of T>A>> C>G, (3) the base-sequence specificity 5(')-GGT/3(')-CCA presented by NA2 is significantly related to recognition of the base pair with the naphthoate moiety, and (4) the different cleavage property between NCS-chr and NA2 is associated with the presence or absence of an aminoglycoside residue. Based on the results of the site-specific cleavage by NA2 for certain bulged DNAs and a fluorescence study of NA2-DNA oligomer complexes, the DNA interaction mode of NA2 has also been examined. These results provide important information to design a new enediyne molecule for a DNA target.

NMR studies of the post-activated neocarzinostatin chromophore-DNA complex. Conformational changes induced in drug and DNA

The glutathione post-activated neocarzinostatin chromophore (NCSi-glu)-DNA complex was studied in detail by 2-D NMR spectroscopy. The complex is a model for understanding the sequence specific cleavage of DNA by the native neocarzinostatin chromophore (NCS chrom), a highly potent enediyne antitumor agent. NMR spectral analysis is presented for the free NCSi-glu, the free DNA duplex and the NCSi-glu-DNA complex. In addition to the previously reported structural details of the complex (Gao, X.; Stassinopoulos, A.; Rice, J. S.; Goldberg, I. H. Biochemistry 1995, 34, 40), we demonstrate that the binding of NCSi-glu in minor groove results in a patch of negatively charged surface covering the otherwise relatively neutral minor groove. The formation of the complex is largely driven by hydrophobic forces and the solvation of the polar surface of the complex. Comparison of the conformations of NCSi-glu and DNA duplex in their free and bound form reveals an induced mutual fit of DNA and NCSi-glu upon complex formation. The reduced NCS chrom represents a DNA binding motif for sequence specific recognition of DNA via intercalation and minor groove interactions.