Ozone-inducible proteins (OI2-2 and OI14-3) from Atriplex canescens whose structure and function are unknown are rich in glycine intercepted with histidine and tyrosine with putative signal peptides at the N-terminus. OI2-2 and OI14-3 contain 8 and 10 tandem repeats of YGHGGG, respectively. In order to study whether these proteins bind Cu2+, circular dichroism (CID), and nuclear magnetic resonance (NMR) were measured for four synthetic peptides corresponding to sections of the sequences of these proteins; 1 (HGGGY), 2 (HGGGYGH), 3 (YGHGGGY), and 4 (YGHGGGYGHGGGY), where all peptides were chemically blocked with an acetyl group at the N-terminus and an -NH2 group at the C-terminus. Visible CID spectra of the four peptides show positive peaks near 580 and 340 nm, which were observed at pH 7.4 but not pH 6.0, indicating clearly that the four peptides bind Cu2+. The NMR spectra indicate that the addition of small amounts Of CuSO4 to 3 (Yl-G2-H3-G4-G5-G6-Y7) causes significant broadening of resonances of the side chain protons, ((CH)-H-beta, (CH)-H-epsilon1, and (CH)-H-delta2) of His3 and the side chain (CH)-H-beta of Tyrl at pH 7.4. In addition, the backbone (CH)-H-alpha resonances of Gly2 and Gly4 were broadened more strongly than those of Gly5 and Gly6. CID titration experiment suggested that two repeats of YGHGGG comprise the fundamental Cu2+ binding unit. Thus, the ozone-inducible proteins are capable of binding at least four or five copper ions per protein. These copper-binding proteins would function as active oxygen scavengers. (C) 2003 Elsevier Inc. All rights reserved.