Attractor Control of the Redox Reactions of Bovine Cytochrome c

Abstract

Although the conformational changes accompanying the oxidation of ferrocytochrome c by the transfer of an electron to cytochrome a are small, they may contribute to the regulation of the electron transfer by transient storage of the liberated energy as strain and atomic vibrations. Both the electron transfer and the conformational changes seem to be controlled by an attractor, i.e. by a manifestation of a deterministic chaos. The putative attractor is regular and is, for the reaction involving the inner monomer of ferricytochrome c (I), of the order of 3.03 ± 0.03. The conformational changes involving the outer monomer of ferricytochrome c (O) seem also to be controlled by a regular attractor, but its order is 4.2 ± 0.2. The low order of the coupled reactions of electron transfer and conformational change suggests that it is essential to the electron transfer process in the respiratory chain. Since the order of attractors of other proteins correlates with the vectorial description of the function (1.0 for myoglobin, 2.0 for chymotrypsin and lysozyme, 3.0 for an abenzyme), the value for cyt. c indicates that not only the electron transfer, but also an additional reaction, e.g. the conformational change, are essential for the function of this protein. Hence, the study of protein attractors may yield information on important details, which could not be obtained by other methods.