Photochemical Sciences Ph.D. Dissertations

Title

Characterization of the Metal Binding Properties of De Novo Designed Coiled Coil Metalloproteins

Date of Award

2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Michael Ogawa

Second Advisor

Rex Lowe (Committee Member)

Third Advisor

George Bullerjahn (Committee Member)

Fourth Advisor

John Cable (Committee Member)

Abstract

The dissertation aims to elucidate three effects on the metal binding properties ofde novo designed coiled coil metalloproteins, which are the stability of the peptide,the placement of the metal binding motif along the peptide sequence, and the variationof the metal binding motif.

Starting from a previously designed peptide C16C19-GGY, a more stable peptide was designed. The new peptide is AQC16C19-GGY. Its Cd(II) complex is a trimer containing 4 Cd(II). In contrast, the Cd(II) complex of C16C19-GGY is a dimer with one Cd(II). The process of the incorporation of Cd(II) into AQC16C19-GGY is shown to be a fast bond formation process followed by a slow conformation change. Therefore, the stability of the peptide affects the metal binding properties.

The effect of the placement of the metal binding motif along the peptide sequence on the metal binding properties was demonstrated by a series of peptides derived from the parent peptide: K(IEALEGK)4GGY. The peptides are C2C5-GGY, C9C12-GGY, C16C19-GGY (the previously studied one), and C23C26-GGY. The Cu(I) binding properties of these peptides were studied and compared. C2C5-GGY and C9C12-GGY have similar metal binding properties. C23C26-GGY has different metal binding properties from those of C2C5-GGY and C9C12-GGY, but its metal binding properties are similar to those of C16C19-GGY. The placement of the metal binding motif along the peptide sequence also plays a role in determining the oligomerization states of the metalloproteins.

In the last chapter, the C-X-X-C metal binding motif was changed to C-X-X-H to study the effect of the first coordination sphere on the metal binding properties. It is seen that the first coordination sphere has an effect on the metal binding properties.Interestingly, one of the obtained metalloproteins shows pH-dependent luminescence properties.

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