What is the nature of the interaction between 2,3-BPG and hemoglobin?

The interaction between 2,3-bisphosphoglycerate (2,3-BPG) and hemoglobin is an important aspect of how hemoglobin regulates its affinity for oxygen. The correct understanding involves recognizing that 2,3-BPG binds to the central cavity of deoxygenated hemoglobin, specifically to the amino acids in the beta chains of the globin. This binding stabilizes the tense (T) state of hemoglobin, which has a lower affinity for oxygen, thereby promoting the release of oxygen from hemoglobin to tissues that need it.

By binding to the globin chain amino acids, 2,3-BPG effectively inhibits the binding of oxygen to hemoglobin. When oxygen levels are high and hemoglobin is fully saturated, the concentration of 2,3-BPG decreases, allowing hemoglobin to transition to the relaxed (R) state with a higher affinity for oxygen. This dynamic helps to regulate oxygen delivery according to tissue demands, supporting the physiological role of 2,3-BPG in oxygen transport and release.

In contrast, the other choices do not accurately describe the interaction: binding to the heme moiety is incorrect as 2,3-BPG does not interact with the iron in heme, simultaneous