Hemoglobin Rainier (HbR) is a mutant in which Tyr 145 of the -globin is replaced by Cys.

Hemoglobin Rainier (HbR) is a mutant in which Tyr 145 of the β-globin is replaced by Cys. This Cys forms an intramolecular disulfide with β Cys93 in the oxy state but cannot form the intramolecular disulfide in the deoxy state. 

(a) How do you expect O₂-binding affinity of disulfide-bonded HbR to compare to that of normal adult Hb (HbA)? 

(b) Do you predict that the Bohr effect for disulfide-bonded HbR is greater than, less than, or the same as the Bohr effect in HbA? In other words, will changes in pH likely have a greater, lesser, or the same effect on O₂ transport by these two Hbs? 

(c) Is a person with disulfide-bonded HbR likely to adapt to higher elevation more slowly or more quickly compared to a person with HbA? (i.e., would HbR be an asset or a liability for someone trying to climb tall mountains?) 

(d) HbR is reported to have P₅₀ = 14 torr and a Hill coefficient = 1.2. Calculate ΔY_O2 for a climber with HbR assuming that, at 14,000 ft (∼ 4300 m), P_O2 = 48 mm Hg in lungs and P_O2 = 15 mm Hg in muscle capillaries. Compare the calculated value of ΔY_O2 for a climber with HbR to ΔY_O2 for a climber with HbA under the same conditions of lung and capillary P_O2. (For HbA: P₅₀ = 28 mm Hg and a Hill coefficient = 3.2.)