Electrochemical and spectroscopic studies of metalloproteins and oxygen activating hemoproteins

Scope and method of study. Proteins play an important role in all biological processes. Redox metalloproteins are proteins whose main function is to act as electron transfer carriers. Often redox metalloproteins act in conjunction with other metalloproteins to supply electrons needed to carry out the enzymatic work necessary for biological function. These proteins can be divided into three main groups according to prosthetic centers: iron sulfur proteins, heme proteins and copper containing proteins. This study consisted of electrochemical and spectroscopic studies of putidaredoxin (an iron sulfur protein), and OM cytochrome b₅ mutants (heme proteins). The first part of the study was the synthesis of the gene coding for Pdx in order to find its direct and reversible electrochemistry via different electrode surfaces and electrochemical techniques. The second part of the study was the design of several axial ligand mutants of OM cyt b5 to study the structural factors that are accountable for channeling oxygen activation toward heme oxygenation.; Findings and conclusions. Part 1: Evidence was found for the factors responsible of modulating the reduction potential of Pdx. It was concluded that when the voltammetry of Pdx is promoted at negatively charged electrodes by a polycation such as polylysine, the reduction potential of Pdx shifts in the positive direction originating from the formation of a transient complex between Pdx and polylysine at the electrode surface. Part 2: Spectroscopic evidence was found showing that the heme oxygenation reaction carried out by HO and the coupled oxidation reaction, which is carried out by other heme proteins and several axial ligand mutants of cyt b₅, proceed by different mechanisms.