Self-assembly of a dimeric β-hairpin peptide mimicking the laccase trinuclear site

Minimal metallopeptide complexes offer simplified yet powerful models of metalloenzyme active sites, enabling the investigation of fundamental structure-function relationships. While α-helical constructs are widely employed for this purpose, β-sheet-based scaffolds remain underexplored. In this work, we leverage the intrinsic symmetry of the trinuclear copper center (TNC) binding pocket in a small laccase to design a β-harpin metallopeptide, LacZip. The construct links β-strands through a tryptophan zipper motif, imparting conformational rigidity to the peptide chain. Spectroscopic analyses, including circular dichroism and fluorescence quenching, demonstrate that LacZip undergoes metal-induced dimerization, reproducing the TNC architecture and binding Cu2+ ions with positive cooperativity. Notably, EPR spectroscopy reveals signals consistent with the formation of a trinuclear Cu3(LacZip)2 complex at high metal concentrations. Overall, our work highlights the potential of β-sheet scaffolds for self-assembly of multinuclear metallopeptide complexes, offering additional tools for the design of stable and functional artificial biomimics.