De Novo Design of Metalloproteins with Variant Hydrophobic Cores

This work studies a series of related de novo designed luminescent Cu(I) metalloproteins having different cysteine-based metal binding sites within the hydrophobic cores. The peptide sequences are based on the (Ia-Eb-Ac-Ld-Ee-Gf-Kg)n heptad repeat which is known to form two-stranded coiled coil in aqueous solution. The metal-binding cysteine residues are placed at the hydrophobic a and/or d positions in the middle of the peptide sequences. With subtle changes of the metal-binding site, the resultant Cu(I) metalloproteins give distinctly different structures and properties. The peptide C16C19GGY exists as a random coil and the Cu(I)-C16C19GGY metalloprotein exists as a 4-helix bundle (Cu4P4, P = peptide) which gives strong room temperature emission at 600 nm. The peptide C12C16GGY exists as a random coil and the Cu(I)-C12C16GGY metalloprotein exists as a 4-helix bundle (Cu4P4) which gives strong room temperature emission at 575 nm. The peptide C12C16C19GGY exists as a random coil and the Cu(I)-C12C16C19GGY metalloprotein exists as a 4-helix bundle (Cu8P4) which gives strong room temperature emission at 605 nm. The peptide C12C19GGY exists as a random coil and the Cu(I)-C12C19GGY metalloprotein also exists as a random coil (Cu4P4) which gives strong room temperature emission at 600 nm. The peptide C16GGY, C19GGY exist as two-stranded coiled-coils and the Cu(I)-C16GGY, Cu(I)-C19GGY metalloproteins exist as 4-helix bundles (Cu3P4) which gives very weak room temperature emission at 603 nm and 630 nm respectively