Knowledge of the parameters controlling the electron transfer reactivity of the redox centers in copper proteins remains elusive despite the wealth of data accumulated over the years. Here, we present the first experimentally based estimate of the reorganization energies of copper(II/I) ions bound to sites which confer on them unique functional properties: type 1 (T1) and type 2 (T2). The former functions as an electron mediator in a wide range of electron carriers and enzymes, while type 2 serves primarily in direct interaction with substrates. Comparing the kinetics of intramolecular electron transfer in copper containing nitrite reductases (CuNiRs), the reorganization energy of the former center is now shown to depend on the symmetry of the coordination sphere, and thus, the more asymmetric flattened tetrahedral T1 site of a green CuNiR gives rise to a smaller reorganization energy (0.6 eV) when compared with the distorted tetrahedral geometry of a blue CuNiR T1 center (0.7-0.8 eV). It is noteworthy that it is still larger than that of the binuclear (purple) Cu-A center, which was found to be 0.4 eV when inserted in a mutated azurin. The tetragonal distortion, possibly arising from small shifts in the loop carrying the Met ligand in the blue and green enzymes, emphasizes the subtle, yet important, role of the protein structure in determining its reactivity.