Hemoglobin efficiently controls the biological activity. Hemoglobin is a tetramer with two alpha chains and two beta chains. Hemoglobin is a symmetrical molecule made up of two assymetrical protomers. The sequence of the myoglobin chains and hemoglobin chains are homologous. But there exist some differences in the region where the chains in hemoglobin contact one another. When hemoglobin binds oxygen to form oxyhemoglobin, there is a change in the quaternary structure. This causes tertiary structure to change by the movement of the proximal histidine. These changes cause the breakage of the constraining salt links between the terminal groups of the four chains. kb
