Question

In a Hemoglobin variant ( HbC ), a His (a positively charged residue) in the BPG binding pocket is replaced by Val (a nonpolar residue).

a. Which state of hemoglobin do you think is favored with this mutant, the T-state or the R-state? Please explain your reasoning.
b. On the same set of axes, sketch the oxygen binding curve for HbA and HbC. Indicate the Kd of HbA and HbC.

Answer 1

With the HbC mutation, the T-state of hemoglobin is favored, and HbA has a higher affinity for oxygen compared to HbC.

Step-by-step explanation:

In a Hemoglobin variant (HbC), a His (a positively charged residue) in the BPG binding pocket is replaced by Val (a nonpolar residue).

a. With this mutation, the T-state of hemoglobin is favored. The T-state is the deoxy state of hemoglobin, where it has a lower oxygen affinity.

b. The oxygen binding curve for HbA and HbC can be plotted as a function of the partial pressure of oxygen in the blood (x-axis) versus the relative Hb-oxygen saturation (y-axis). The Kd of HbA is lower than that of HbC, indicating that HbA has a higher affinity for oxygen.