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
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.