At pH 7 the binding of 2,3-BPG to hemoglobin occurs at which site?

2,3-BPG Stabilizes the T Structure of HemoglobinA low Po2 in peripheral tissues promotes the synthesis of 2,3-bisphosphoglycerate (BPG) in erythrocytes. The hemoglobin tetramer binds one molecule of BPG in the central cavity formed by its four subunits (Figure 6-6). However, the space between the H helices of the b chains lining the cavity is sufficiently wide to accommodate BPG only when hemoglobin is in the T state. BPG forms salt bridges with the terminal amino groups of both b chains Val NA1 and with Lys EF6 and His H21.Ref: Harper&;s Biochemistry; 30th edition; Chapter 6 Proteins: Myoglobin & Hemoglobin