CYCLIC VOLTAMMETRY OF IMIDAZOLEMICROPEROXIDASE-8 - MODELING THE CONTROL OF THE REDOX POTENTIAL OF THE CYTOCHROMES

A number of cytochromes have midpoint redox potentials that are strongly dependent upon pH; these include the bacterial cytochromes C21,2and both cytochrome b-5623and the cytochrome d terminal oxidase complex of Escherichia coli.4NMR and other spectroscopic evidence has shown, at least for the cytochromes c2, that the redox potential is controlled by the state of ionization of a heme propionate or a noncoordinated imidazole of a His residue in close proximity to the iron porphyrin.1This provides an example of how proteins couple changes at one site (±e-at Fe) to changes at another site (±H+at an ionizable functional group), an effect that may be relevant, for example, to the proton-pumping activity of various components of the respiratory chain and physiological control of electron transport.4-8. © 1990, American Chemical Society. All rights reserved.