Photochemical Sciences Ph.D. Dissertations

Metal-binding Properties of Synthetic Metalloproteins

Date of Award

2005

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Michael Ogawa

Abstract

This dissertation describes the metal-binding properties of synthetic self-assembled metalloproteins. A family of the synthetic metalloproteins was prepared based on the de novo designed peptide C16C19-GGY having the sequence Ac-K(IEALEGK)2(CEACEGK)(IEALEGK)GGY-amide. This sequence is based on the IEALEKG heptad repeat known to form two-stranded á-helical coiled coils, but was modified to contain the Cys-X-X-Cys thiolato metal binding motif found in a variety natural of metalloproteins. This cysteine-containing random coil apopeptide is capable of binding a variety of soft metal ions such as, Cu(I), Cd(II), Ag(I), Hg(II), Au(I), and Pt(II) which results in the formation of a metal-bridged self-organized á-helical bundles. It has been shown that such binding produces metal-specific oligomerization states of the resulting metalloproteins: synthetic Cu(I), Ag(I), Au(I), and Pt(II)-metalloproteins have an oligomerization state which differs from the one predicted by original design. These inorganic cofactors not only induce peptide self-assembly, but direct and transform the oligomerization state of the peptide. This illustrates how the structures of metalloproteins may be controlled by the coordination chemistry of their inorganic cofactors. A 1:1 metal:peptide stoichiometry is observed for the Cu(I) and Ag(I) adducts but the Cd(II) and Hg(II) complexes show a metal:peptide stoichiometry of 1:2. It is also shown that the Cu(I)-metalloprotein described here displays an intense room temperature long-lived (microsecond) luminescence at 600 nm. Such incorporated chemical functionality allows using this synthetic metalloprotein as a photoinduced electron-transfer agent in future studies.

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