SPECIFIC INTERACTIONS OF BOVINE AND HUMAN BETA-CASOMORPHIN-7 WITH CU(II) IONS

Complex formation between Cu(II) and human and bovine beta-casomorphin heptapeptides. Tyr-Pro-Phe-Val-Glu-Pro-Ile and Tyr-Pro-Phe-Pro-Gly-Pr o-Ile, respectively, was investigated by pH potentiometry and spectros copic (CD, EPR and electronic absorption) techniques. The results show ed the critical impact of Pro residues on the complex equilibria forme d. The presence of the Pro residue at the second position leads to for mation of very stable dimeric species in which two metal ions co-ordin ate to N-terminal {NH2,C=O} binding sites of one peptide molecule and the deprotonated phenolic oxygen of the second ligand molecule. The pr esence of two additional hydrophobic residues on the C-terminal makes heptapeptide molecule much more effective ligand than its pentapeptide N-terminal fragment. (C) 1998 Elsevier Science Inc. All rights reserv ed.