Comparison of the Kinetics and Spectral Properties of AuCl4- Binding by Methanobactins from Methylosinus trichosporium OB3b and Methylocystis Strain SB2: Evidence of Exciton Disruption between Intramolecular Chromophores

Turpin, Erick
Major Professor
Alan DiSpirito
Committee Member
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Biochemistry, Biophysics and Molecular Biology

Methanobactin (Mb) is the first characterized example of a chalkophore or copper

binding protein. Mbs are produced by most aerobic methane oxidizing bacteria for Cu

recruitment to the cell and eventually incorporation into the central metabolism. In addition to

the biological purpose of Cu binding, mbs bind a number of transition and near transition metals.

Within this text, the metal binding properties are explored and compared between two mbs,

which represent two distinct groups of mbs, mb from Methylosinus trichosporium OB3b and mb

from Methylocystis strain SB2. The Cu binding properties of these mbs have been previously

explored, however, herein, the binding and displacement properties of each mb are presented for

a number of transition metals.

The binding properties of the metals able to displace Cu from Cu bound mb (Cu-mb) are

of particular interest due to the extremely high affinity with which mbs bind Cu. Mercury is one

such example, and the binding properties of Hg, in the forms Hg2+, Hg(CN)2, and CH3Hg+, are

examined for mb from Methylocystis strain SB2. Each form was bound slightly differently by

mb-SB2. Chapter 2 presents the characterization of the Hg binding, in each form, for mb-SB2.

Au also displaces Cu-mb for both mb-OB3b and SB2. In the final chapter, the Au

binding properties of mb-OB3b and mb-SB2 are compared. Previously collected CD spectra of

mb-SB2 titrated with Au(III) suggested that an exciton transfer exists between the chromophores

of mb-SB2. Herein, stopped flow UV-vis kinetic traces of mb-OB3b titrated with Au(III)

demonstrate that an exciton transfer is present between the chromophores of mb-OB3b.