Hemoglobin Gallery of still pictures and animations. Monomeric Binds 1 oxygen molecule. Non-cooperative binding of O 2 . Alters conformation of Fe at unliganded sites. Allosteric effects occur when the binding properties of a macromolecule change as a consequence of a second ligand binding to the macromolecule and altering its affinity towards the first, or primary, ligand.
Allosteric effects are important in the regulation of enzymatic reactions.
Allosteric effects require the presence of two forms of the macromolecule. The other form, usually called the R or relaxed state, binds ligand with high affinity. The T and R states are in equilibrium with each other. In the case of positive cooperativity the fraction of T states exceeds that of the R state. Heterotropic Allosteric Effectors in Hemoglobin.