Complex formation by peptides containing more than one prolyl residue; some unexpected trends with biological implications

Abstract

Pentapeptides of general formula X-Pro-X-Pro-X are unable to co-ordinate to Cu^II through any of the peptidenitrogen atoms while those of formula X-Pro-Pro-X-X form stable, chelated complexes with 2N co-ordination and a large chelate ring; however with X-Pro-Lys-Pro-X (Substance P_1–5) and Substance P itself the ε-amino-N of the Lys residue participates in co-ordination, forming a large, stable chelate ring.