Non-allosteric cooperativity in hemoglobin
Hemoglobin (Hb) is the prototypical example of a cooperative protein. Cooperativity of Hb is largely accounted for by an allosteric structural change between the T and R quaternary structures. Allostery is such a powerful explanation of Hb cooperativity that the possibility of cooperative events occurring within each allosteric conformation, in the absence of any quaternary structural change has usually been overlooked, and actually experiments specifically aimed at detecting non-allosteric cooperativity have usually failed to do so.