title: Iron-bleomycin-deoxyribonucleic acid system. Evidence of deoxyribonucleic acid interaction with the alpha-amino group of the beta-aminoalanine moiety.
abstract: The Fe(III) complex of bleomycin (BLM) is, at pH 4, in the high-spin form. At pH 7, the coordination of the alpha-amino group of the beta-aminoalanine moiety of BLM converts it to a low-spin species: BLM X Fe(III) X alpha NH2. The conversion of the high-spin species to the low-spin one can also take place at pH 4 (i) by addition of ligands L such as N3-, S2O3(2-), and SCN- or (ii) through interaction with DNA. Moreover, the addition, at pH 7, of DNA to BLM X Fe(III) that has been previously complexed with one of these ligands L displaces this latter from its position. These results suggest that (i) the ligand L occupies the same site of coordination as the alpha-amino group and (ii) an interaction occurs between the beta-aminoalanine moiety of BLM and DNA that lowers the pKd of the alpha-amino group, promoting its coordination to iron.
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives*; D000818:Animals; D001665:Binding Sites; D001761:Bleomycin / Q000031:analogs & derivatives; D002417:Cattle; D002942:Circular Dichroism; D004247:DNA; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011199:Potentiometry; D011485:Protein Binding; D011487:Protein Conformation; D013950:Thymus Gland; D015091:beta-Alanine / Q000031:analogs & derivatives*
chemical_list: C023503:iron bleomycin; D001761:Bleomycin; D015091:beta-Alanine; C011757:2,3-diaminopropionic acid; D004247:DNA; D000409:Alanine