Naked mole rats were recently discovered to be able to survive18 minutes of an anoxic (0% oxygen) environment without anydifficulty. In 1976, the naked mole rat hemoglobin was studied andcompared to that of mice and found to have higher oxygen affinity.The data below are representative of this study.

Table 1: Whole blood from each organism was assayed at pH 7.4for oxygen affinity at two different temperatures. TheP₅₀ is reported at each condition in the table.

Species	30°C	37°C
Heterocephalus glaber	18.8mmHg	23.3mmHg
Mus musculus	24.9mmHg	33.0mmHg

Naked mole rats have a body temperature of 30-32°C, which islower than the 37°C body temperature of most other mammalsincluding Mus musculus.

A. Quickly look up data regarding the solubility of oxygen inwater versus temperature. Does body temperature alone explain thegreater oxygen binding capacity of Heterocephalus glabercompared to Mus musculus?

B. What do these p50 values indicate about the oxygen bindingcapacity of Heterocephalus glaber hemoglobin compared toMus musculus hemoglobin?

C. Furthermore, the amount of 2,3-BPG in each organism’sbloodstream was assayed. [2,3-BPG] in Heterocephalusglaber was found to be 7.3mM and for Mus musculus,7.4mM. Additionally, when hemoglobin from each organism wasstripped of any ligands and then assayed for oxygen binding, thep50 for Heterocephalus glaber was found to be 8.0mmHg andthe p50 for Mus musculus was found to be 11.3mmHg. What dothese data tell you about the mechanism by which the affinity ofeach organism’s hemoglobin differs?

D. The protein sequence for the b-subunit of the naked mole rathemoglobin is as follows:

HLSNE EKAAV TSLWG KVNVE ETGGE ALGRL LVVYP WTQRF FEHFG DLSSPSAIMG NPKVK AHGAK VLASF SEGLN HLDNL KGTFA KLSEL HCDKL HVDPE NFRLLGNVIV IVLAH HHGHD LTPTV QAAFQ KVVAG VAHAL GHKYH

Note that the actual structure of hemoglobin or the actualprotein and mRNA sequences of other subunits of hemoglobin in thenaked mole rat have not been studied. The mRNA informationavailable is predicted from genome sequencing efforts, but has notbeen experimentally verified or studied.

What is the significance of the shaded amino acids? Hint, useyour book. Are there any major differences in the two sequencesthat might explain the phenotype? Do not spend too much timeagonizing over this.