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Change in distal his in hemoglobin

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Change in distal his in hemoglobin

Postby tntran » Fri Oct 16, 2009 3:09 pm

Hi I been trying to this problem but not quite sure how to approach this problem from my study guide for biochemistry

Hemoglobin is the molecule responsible for movement of oxygen from the lungs to the tissues. Thus far in our class we have discussed several important structural features that are directly related to this function. Furthermore, we have discussed the importance of the distal His (His64) in myoglobin with respects to carbon monoxide binding. Hemoglobin subunits also each have a distal His (His58 for α and His63 for β) that functions in precisely the same manner as in the myoglobin residue. In the space below I would like you to draw the carbon monoxide and oxygen binding curves of hemoglobin consisting of:

1. Normal subunits
2. Subunits with a distal His that has been mutated to Gly (Label as His-to-Gly). Note that all the subunits contain this mutation.
3. Subunits with a distal His that has been mutated to Trp (Label as His-to-Trp). Note that all the subunits contain this mutation.
4. NOTE: Each graph should have 3 separate curves for each of the conditions described above, make sure you distinctly label them!

I know that when CO is added it creates a sterically hinderance to the distal his. So its forced to change its angle making it have lower affinity then a free heme. But i cant figure how to graph it with different amino acid, and hemoglobin has a sigmoidal curve. Any help will be appreciated.
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Postby mith » Fri Oct 16, 2009 9:05 pm

it's asking whether you'd expect the mutant to have similar properties to His, considering the factors affecting His are steric.
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