In cooperative binding, what happens after one subunit of hemoglobin transitions from T-state to R-state?

In cooperative binding, hemoglobin exhibits a phenomenon where the binding of oxygen to one subunit influences the affinity of the remaining subunits for oxygen. When one subunit transitions from the T-state (tense state) to the R-state (relaxed state) upon binding oxygen, it induces a conformational change that makes the other subunits more likely to transition to the R-state as well.

This dramatic change occurs because the transition of one subunit alters the overall structure of hemoglobin. In the R-state, the hemoglobin has a higher affinity for oxygen, and the structural change promotes a cascading effect. As one subunit binds oxygen and moves to the R-state, the other subunits experience increased likelihood of binding additional oxygen molecules due to this enhanced affinity.

Thus, once one subunit is in the R-state, it effectively stabilizes the R-state conformation of the remaining subunits, facilitating more efficient oxygen loading in the lungs. This illustrates the principle of cooperativity in hemoglobin, where early binding events enhance the likelihood of subsequent bindings, leading to an efficient delivery of oxygen throughout the body.