Capreomycin — A polypeptide antitubercular antibiotic with unusual binding properties toward copper(II)

Capreomycin is an important therapeutic agent having intriguing and diverse molecular features. Its polypeptidic structure rich in nitrogen donors makes the drug a promising chelating agent for a number of transition metal ions, especially for copper(II). The results of the model investigational studies suggest that capreomycin anchors Cu2+ ion with an amino function of the α,β-diaminopropionic acid residue at pH around 5. At physiological pH copper(II) ion is coordinated by two deprotonated amide nitrogen atoms of the α,β-diaminopropionic acid, the serine residue as well as the amino function deriving from the β-lysine. Above that pH value we observe a rearrangement within the coordination sphere leading to movement of Cu2+ to the center of the peptide ring with concurrent coordination of four nitrogen donors. Spin–lattice relaxation enhancements and potentiometric measurements clearly indicate that deprotonated amide nitrogen atom from the β-ureidodehydroalanine moiety is the fourth donor atom.

Graphical abstractCapreomycin, a polypeptide antibiotic is active against certain strains of tuberculosis. It is able to bind Cu2+ in the center of the cyclic polypeptide ring tightly. High stability of the complex suggests its potential occurring in physiological conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide