CHEMICAL AND PHYSICAL STUDIES OF TWO BACTERIAL FERREDOXINS.
Item
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Title
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CHEMICAL AND PHYSICAL STUDIES OF TWO BACTERIAL FERREDOXINS.
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Identifier
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AAI8203301
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identifier
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8203301
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Creator
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MAGLIOZZO, RICHARD S.
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Contributor
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William V. Sweeney
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Date
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1981
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry
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Abstract
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The thesis is primarily composed of an investigation of the pH dependence exhibited by the midpoint reduction potential of Clostridium pasteurianum 2(4Fe-4S) ferredoxin. The experiments described involve the determination of the E(, 1/2) vs. pH behavior in buffer with high ionic strength and an examination of the dependence of nmr, epr and CD spectra on pH. The results of the spectroscopic investigations indicate that the protein does not exhibit a pH dependent conformation equilibrium suggesting that the pH effect arises from oxidation state dependent hydrogen ion equilibria. The data fit a model describing two equivalent sites of protonation per molecule of ferredoxin, each with a pK = 7.4 in the oxidized form and a pK = 8.9 in the reduced form. These proton equilibria may be assigned to the 4Fe-4S centers in this ferredoxin. Such a result is consistent with known properties of iron-sulfur proteins (including hydrogenase) and is likely to be a general feature of the chemistry of iron-sulfur centers. It is suggested that the involvement of iron-sulfur protein centers in energy conservation at Site I in mitochondrial electron transport may represent a specialization of the observed oxidation state dependent hydrogen ion equilibrium. The thesis also contains preliminary studies of the reconstitution of iron-sulfur centers in Azotobacter vinelandii Fd I and in a synthetic tridecapeptide. The details of a synthetic route to a water soluble 4Fe-4S model compound and an attempt to form a CO adduct of ferredoxin are also described. The effect of DMSO and EDTA on A. vinelandii Fd I is described. Appendix I is entitled "Study of the Influence of NH(.)(.)(.)S Hydrogen Bonds on the Reduction Potential in Clostridium pasteurianum 2(4Fe-4S) Ferredoxin Using Deuterium Exchange", W. V. Sweeney and R. S. Magliozzo, and appears in Biopolymers 19: 2133 (1980). The experiments described there concern the deuteration of both slowly and rapidly exchanging protons and subsequent measurement of midpoint reduction potentials in the derivatives. The results indicate that hydrogen bonding from amide donors to sulfurs in the iron-sulfur centers does not significantly affect the reduction potential of the ferredoxin.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biochemistry
