The protein mechanism for the electron transfer of rubredoxin occurs in two steps. The first protein effect, is through the expansion of iron-sulfur bond lengths upon reduction and the shortening of hydrogen bond lengths ensure a better electrostatic stabilization of the negative charge. The other protein effect, is gating mechanism which is created from the conformational changes of Leucine 41. The leucine 41 has a non-polar side chain that allows for transient penetration of the water molecules. This increases the polarity of the redox site environment. The Leucine 41 side chain has two different conformations; reduced and the oxidized form. The conformation in the reduced form is open and allows water molecules near the [Fe(S-Cys)4] 2+ active site and stabilizing the higher net positive charge of the reduced Fe 2+ oxidation state. This shifts the potential 50 mV more positive as indicated by Leucine 41 – Alanine site directed mutagenesis shift of the Fe 3+/2+ redox potential 50 mV more positive. The conformation allows for the infiltration of water molecules which lets the formation of the strongly Hydrogen-bond to attach.