Question

Is the P₅₀ higher or lower than normal in (a) hemoglobin Yakima and (b) hemoglobin Kansas? Explain.

Short answer

The P₅₀ value is lower than normal in (a) hemoglobin Yakima and higher than normal in (b) hemoglobin Kansas.

Step-by-step solution

Hemoglobin Yakima

In the hemoglobin variant Yakima, the amino acid Asp (99) is mutated to His. This mutation disrupts a hydrogen bond that stabilizes the T conformation of hemoglobin.

T conformation of hemoglobin represents the deoxyhemoglobin state. Hence, stabilizing the deoxy-conformation represents a reduction in the oxygen affinity of hemoglobin. Thus, the P₅₀ value of the variant becomes lower than normal.

Hemoglobin Kansas

In the hemoglobin variant Kansas, the amino acid Asn (99) is mutated to Thr. This mutation disrupts a hydrogen bond that stabilizes the R conformation of hemoglobin.

R conformation of hemoglobin represents the oxyhemoglobin state. Hence, stabilizing the oxy-conformation represents an increase in the oxygen affinity of hemoglobin. Thus, the P₅₀ value of the variant becomes higher than normal.