The mutation in hemoglobin at 82 Lys Asp results in lowered O2-binding affinity compared to normal

The mutation in hemoglobin at β82 Lys → Asp results in lowered O2-binding affinity compared to normal hemoglobin. β82 is one of the residues that lines the 2,3-BPG binding site. Based on the location of this residue and the differences between Lys and Asp, suggest a rationale for the observed reduction in O2-binding affinity.