De novo peptide design allows for the manipulation of metal binding coordination spheres within native like protein environments. An alpha helical trimer of the general sequence G-LKALEEK5-G has been synthesized with both a Cys3 Pb(II) and a His3 transition metal binding site. The binding of lead(II) to the three cysteine residues ensures heterotrimer formation. Co(II) binds to the imidazole nitrogens of three histidine residues, but this coordination sphere can be manipulated by introducing aspartate or glutamate residues in close proximity to the histidine residues. Molecular models predict that the aspartate residue is far away from the plane of the His residues for the metal to coordinate all three histidine residues and the carboxylic acid, but the increased length of the glutamate residue may allow for direct coordination of both oxygen of the carboxylic acid and all three imidazole rings. Previous work on aspartate heterotrimers and preliminary UV-Vis spectroscopy of glutamate heterotrimers suggest asymmetric imidazole/carboxylic acid binding providing a mixed primary coordination sphere of the Co(II). The integrity of the heterotrimers containing glutamate resides will be assessed using 207Pb NMR and perturbations of the Co(II) binding site will be further investigated via EPR, UV-Vis, and CD experiments. The generation of asymmetric binding sites will allow for more complex models of native systems that are known to utilize asymmetric catalytic centers.

Glutamate induced asymmetric binding of transition metals in de novo designed helical heterotrimers

251st National Meeting (2016)

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