Binding processes in hemeproteins involve the iron atom and the protein properties: structural and dynamics. Crystallographic data of Perutz have given an appreciate popularity to a correlation between the displacement of the iron out of the porphyrin plane and the affinity of the hemeprotein for ligand. However, the dynamics character of the protein matrix may explain the ligand binding properties in hemeproteins. The internal motions of the apoprotein could be “the structural parameter” involved in the mechanism regulating the ligand binding.