ABSTRACT
Many metal ions play decisive roles in living organisms ranging from bacteria to mammals. The copper ion is essential in several biological systems and, with the exception of the large multisubunit copper protein, haemocyanin, which transports molecular oxygen in a variety of invertebrates, all copper proteins are in one way or the other involved in electron transfer (ET). In ‘blue’ copper proteins and copper-containing oxidases, intramolecular ET becomes the fundamental physical event through which specificity and control is exerted. This chapter deals with long range electron transfer in the above types of copper proteins. In all the copper-containing ET proteins, the metal is relatively inaccessible for external reactants or solvent molecules, which then raises the fundamental question as to how electrons proceed to and from the copper ion. Mutant studies on Azurin show that ET between Az and nitrite reductase takes place via the hydrophobic patch, with the copper ligand His117 serving as electron conductor.
