2,3-Bisphosphoglycerate (2,3-BPG) is an important regulator of hemoglobin oxygen affinity. Which statement best describes its mechanism of action?

• A It binds covalently to the heme iron, preventing oxygen binding
• B It binds to the central cavity of deoxyhemoglobin (T-state), stabilizing it and reducing oxygen affinity ✓
• C It competes with oxygen for binding to the proximal histidine residue
• D It binds preferentially to the R-state (oxygenated) conformation, increasing oxygen affinity

Explanation

2,3-BPG binds in the central cavity between the two beta chains of deoxyhemoglobin, interacting with positively charged residues (His2, His143, Lys82) and stabilizing the T-state. This reduces oxygen affinity, shifting the ODC rightward and facilitating oxygen release to tissues. Option D is wrong because 2,3-BPG binds the T-state, not the R-state.

Reference: Lehninger Principles of Biochemistry, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.