Acta Biochimica Polonica 51(1), 93-106

Effect of tetrazole moiety on coordinating efficiency of deltorphin.

Elzbieta Lodyga-Chruscinska1, e-mail, Stanislaw Oldziej2, Giovanni Micera3, Daniele Sanna4, Longin Chruscinski5, Jacek Olczak6 and Janusz Zabrocki6

1Institute of General Food Chemistry, Technical University of Lodz, Lodz, Poland; 2Faculty of Chemistry, University of Gdansk, Gdansk, Poland; 3Department of Chemistry, University of Sassari, Sassari, Italy; 4Istituto C.N.R. Chim. Biomolecolare, Sassari, Italy; 5Faculty of Process and Environmental Engineering, Technical University of Lodz, Lodz, Poland; 6Institute of Organic Chemistry, Technical University of Lodz, Lodz, Poland

Key words: opiod peptides, tetrazole analogues of deltorphin I, Cu(II) complexes

 A study of the effect of the tetrazole moiety, a cis-amide bond surrogate, on the Cu(II) coordinating properties of oligopeptides is reported. Insertion of the tetrazole moiety Ψ[CN4] into the peptide sequence of [D-Ala2]deltorphin I changes considerably the coordination ability of the peptide. Potentiometric and spectroscopic results show that if the tetrazole moiety is in a suitable position in the peptide chain, i.e. it follows the second residue, a stable CuL species involving 3N coordination is formed in the physiological pH range. The tetrazole Ψ[CN4] ring provides one of these nitrogens. The data indicate that Cu(II) ions are strongly trapped inside a bent peptide backbone. The peptide conformation changes achieved by Cu(II) coordination may be essential for the binding of tetrazole deltorphins at opiate receptors.

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