Energy saving electron pathways in proteins.

This paper is a contribution to the discussion of whether the general architecture of electron transfer sites in blue copper proteins is mainly a result of the structural preferences of the metal ion or is induced by the protein. Although the site is probably stable only when protected by the protein, there appears to be no strain from the latter on the structure in the vicinity of the copper atom. For an operative redox site it is further required that the geometry of the site is acceptable for both oxidation states, to avoid high reorganization energy. The site must also be connected to the outer world by suitable tunneling pathways. The blue copper sites appear to fulfill these requirements, but it is difficult to assess the role of evolutionary pressure to form electron transfer proteins in general.