Regulation of Electron Transfer in Metalloproteins

The close functional interplay between the prosthetic group and the polypeptide chain in redox enzymes is the theme of this paper, and re— presents a natural extension of the well established regulation exerted by the protein mojety on the ligand binding properties of hemoglobins and other oxygen carriers. Two relevant examples are discussed: in the first one (azurin) the mole— cular mechanism controlling the electron transfer reactions is restricted to the immediate chemical environment of the metal center, while in the second one (mitochondrial cytochrome oxidase) it involves a conformational transition of the whole quaternary structure of the enzyme. The power of the kinetic approach in detecting significant intermediates is emphasized.