TY - JOUR
T1 - Copper Environment in Artificial Metalloproteins Probed by Electron Paramagnetic Resonance Spectroscopy
AU - Flores, Marco
AU - Olson, Tien L.
AU - Wang, Dong
AU - Edwardraja, Selvakumar
AU - Shinde, Sandip
AU - Williams, Joann
AU - Ghirlanda, Giovanna
AU - Allen, James
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/10/29
Y1 - 2015/10/29
N2 - The design of binding sites for divalent metals in artificial proteins is a productive platform for examining the characteristics of metal-ligand interactions. In this report, we investigate the spectroscopic properties of small peptides and four-helix bundles that bind Cu(II). Three small peptides, consisting of 15 amino acid residues, were designed to have two arms, each containing a metal-binding site comprised of different combinations of imidazole and carboxylate side chains. Two four-helix bundles each had a binding site for a central dinuclear metal cofactor, with one design incorporating additional potential metal ligands at two identical sites. The small peptides displayed pH-dependent, metal-induced changes in the circular dichroism spectra, consistent with large changes in the secondary structure upon metal binding, while the spectra of the four-helix bundles showed a predominant α-helix content but only small structural changes upon metal binding. Electron paramagnetic resonance spectra were measured at X-band revealing classic Cu(II) axial patterns with hyperfine coupling peaks for the small peptides and four-helix bundles exhibiting a range of values that were related to the specific chemical natures of the ligands. The variety of electronic structures allow us to define the distinctive environment of each metal-binding site in these artificial systems, including the designed additional binding sites in one of the four-helix bundles.
AB - The design of binding sites for divalent metals in artificial proteins is a productive platform for examining the characteristics of metal-ligand interactions. In this report, we investigate the spectroscopic properties of small peptides and four-helix bundles that bind Cu(II). Three small peptides, consisting of 15 amino acid residues, were designed to have two arms, each containing a metal-binding site comprised of different combinations of imidazole and carboxylate side chains. Two four-helix bundles each had a binding site for a central dinuclear metal cofactor, with one design incorporating additional potential metal ligands at two identical sites. The small peptides displayed pH-dependent, metal-induced changes in the circular dichroism spectra, consistent with large changes in the secondary structure upon metal binding, while the spectra of the four-helix bundles showed a predominant α-helix content but only small structural changes upon metal binding. Electron paramagnetic resonance spectra were measured at X-band revealing classic Cu(II) axial patterns with hyperfine coupling peaks for the small peptides and four-helix bundles exhibiting a range of values that were related to the specific chemical natures of the ligands. The variety of electronic structures allow us to define the distinctive environment of each metal-binding site in these artificial systems, including the designed additional binding sites in one of the four-helix bundles.
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U2 - 10.1021/acs.jpcb.5b04172
DO - 10.1021/acs.jpcb.5b04172
M3 - Article
C2 - 26201933
AN - SCOPUS:84946047787
SN - 1520-6106
VL - 119
SP - 13825
EP - 13833
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 43
ER -