Biomimetic Pseudopeptides to Decipher the Interplay between Cu and Methionine-Rich Domains in Proteins.

Maintaining tightly copper homeostasis is crucial for the survival of all living organisms, in particular microorganisms like bacteria. They have evolved a number of proteins to capture, transport and deliver Cu(I), while avoiding Fenton-like reactions. Some Cu proteins exhibit methionine-rich (Met-rich) domains, whose role remains elusive. In this work, we designed biomimetic compounds recapitulating the possible Cu(I) binding sites in these domains, in order to examine the parameters important for Cu(I) binding. Five different biomimetic pseudopeptides were synthesized, exhibiting either three methionines or two methionines and a third amino acid likely to be present in the Met-rich domain. The affinities for Cu(I) of these model binding sites were determined, as well as their redox properties and behavior in the presence of Cu(II). Our results highlight the importance of Met residues, and their abundance in Met-rich domains, to efficiently bind Cu(I) in the periplasmic space.