Biology 3601 Fall 2013

Non-cooperativity occurs when the bindng of multiple ligands to a protein are independent of one another (there is a single KD for all ligands).

Hemoglobin Subunit Interactions

Oxygen Binding to Hemoglobin

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Cooperativity_from_Allostery'>Hemoglobin Conformations

(Tense state = low O2)

(Relaxed state = high O2)

Cooperativity from Allostery

Allostery – when the binding of a ligand to one site in a macromolecule affects the binding to another site in the macromolecule

Cooperativity

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Cooperativity

The sigmoidal shape of the hemoglobin–oxygen binding curve can be explained if hemoglobin has two distinct conformations, each with their own affinity for oxygen. At low oxygen saturation, hemoglobin is in the conformation that binds oxygen poorly. As the concentration of oxygen increases, the hemoglobin shifts to a conformation that binds oxygen more tightly.