Can the alpha-hydroxymethylated amino acid residue influence the peptide binding ability towards copper(II) ions?

Complexing ability of tetrapeptides Phe- (R,S)HmR-Arg-Lys, Phe-(R)HmR-Arg-L ys and Phe-(R,S)HmO-Arg-Lys containing potential multi-donor systems provid ed by the novel amino acid alpha-hydroxymethylarginine or by alpha-hydroxym ethylornithine has been investigated by potentiometry and the spectroscopic methods (EPR, UV-VIS and CD). Their complexes with copper(ll) ions were co mpared with those of the parent peptides Phe-Ala-Ala-Lys, Phe-Ser-Ala-Lys, Phe-Arg-Arg-Lys and Phe-Orn-Arg-Lys. The significant enhancement of thermod ynamic stability is observed for the 2N and 3N species. The CD and EPR spec tra support square-planar geometry in 3N species formed at physiological pH . The distortion of the metal environment is induced through the bend confo rmation adopted by the peptide molecule. The Lys residue is the critical fa ctor influencing this geometry distortion in the 3N species. However, the p resence of a alpha-hydroxymethyl group affects the stability of the complex es, most likely by stabilizing conformations suitable for metal complexatio n, (C) 1998 Elsevier Science Inc. All rights reserved.