Question

The mutation in hemoglobin at β82Lys→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 (see the figure above; β82 is adjacent to His143).

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. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer.

Asp positive T negative R (−)-charged (+)-charged Lys

QUESTION:

The ----- charge on the --- side chain can form salt bridges with the other --- side chains in the BPG-binding pocket and stabilize the __-state. In essence, the _ side chain is mimicking the _ charge on BPG.

choices to pick from: R, (+)-charged, (-)-charged, Asp, negative, positive, Lys, T

Answer 1

Answer

1. Negative,

2. Asp,

3. (+) -charged,

4. T,

5. Asp,

6. Negative

The negative charge on the Asp side chain can form salt bridges with the other (+) -charged side chains in the BPG-binding pocket and stabilize the T-state. In essence, the Asp side chain is mimicking the negativecharge on BPG.