Erman, James E.
Ph.D. (Doctor of Philosophy)
Department of Chemistry and Biochemistry
In this dissertation the ability of a protein matrix to modulate protein reduction potential is examined. Protein matrix effects are examined through reduction potential measurement of single, double, and triple mutants of the heme protein cytochrome c peroxidase. Hemes are protein prosthetic groups composed of a single iron chelated in the center of a porphyrin ring. Proteins with heme groups have a large range of functionalities due to the capacity of the heme group itself to exhibit a wide range of chemical reactivity as well as the ability of the iron to change oxidation state. The variety of function seen in heme proteins is due to the ability of the protein matrix surrounding the heme to modulate the electrochemical characteristics of the heme iron. From a functional perspective, the delocalization of the electrons in the porphyrin ring, the different adopted structures of the surrounding protein matrix, and the wide variety of possible interactions with nearby amino acid residues allows the heme group to have a wide range of reduction potentials in different proteins. Structure function relationships on the control of reduction potentials and redox properties have been the subject of research for over 30 years. Specifically these studies have focused on the following factors: substituent groups on the porphyrin ring, axial ligation to the iron, the hydrophobic environment and electrostatic effects, and the solvent access to the heme center. Despite the growing wealth of information on heme reduction potentials, the ability to predict the reduction potential based on structure alone has had only limited success. A long-term goal in the field of heme protein chemistry is to elucidate the structural determinants of reactivity. However, the immediate goals of the research project described in this dissertation are to investigate the effects of distal pocket mutations on the Fe(II)/Fe(III) redox couple in cytochrome c peroxidase, investigate the effects of surface mutations on the Fe(II)/Fe(III) redox couple, and determine whether protonation of the His-52 in the Fe(II) state is responsible for the pH dependence of the reduction potential of CcP.
DiCarlo, Cory M., "Reduction potential measurement as a method to elucidate the structure-function relationship in the heme protein cytochrome c peroxidase" (2003). Graduate Research Theses & Dissertations. 4668.
xiii, 306 pages
Northern Illinois University
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