RECENT PROGRESS IN THE ELECTROCHEMISTRY OF C-TYPE CYTOCHROMES

C-type cytochromes are classified into two main groups: i) cytochromes which give fast electrochemical responses at the conventional electro des in the absence of any promoter leg multi-heme cytochromes c(3)); i i) cytochromes which need the presence of promoters or the use of modi fied electrodes to exhibit fast electrochemical responses leg one-heme mitochondrial cytochrome c). In the latter case, careful design of el ectrode surface and composition of the solution are required for the a ttainment of rapid and reversible electron-exchange reactions. Some ge neral considerations are given on the 'electrochemical model'. In part icular, binding interactions between the electrode and the protein can take place in a similar manner to that occurring between physiologica l partner proteins. Electrochemistry when coupled to other physical te chniques can give more complete insights in the relationship between t he redox properties, structure and function of c-type cytochromes. In particular, in the case of polyheme cytochromes, promising results are expected from the study of site-directed mutagenesis-modified cytochr ome c(3).