Hemoglobin a) How many subunits make up the quaternary structure of hemoglobin?

Question

Hemoglobin

a) How many subunits make up the quaternary structure of hemoglobin?

b) How many oxygen molecules can hemoglobin bind to at one time?

c) Why is it initially hard for the first oxygen to bind to hemoglobin?

d) What is the purpose of the depicted histidine amino acid in hemoglobin? How is it interact with the iron atom?

e) Which atom on the histidine amino acid is directly interacting with the iron atom?

f) Would the same interaction occur if the histidine amino acid was replaced by leucine? Explain

Explanation / Answer

(a). Four subunits make up the quaternary structure of hemoglobin

(b). Four oxygen molecules can hemoglobin bind to at one time

(c). Initially the four subunits are located away from one another. The first binding of oxygen is difficult because there is no recieving change in globin strucutre intially, but after one oxygen is bound, the changed protein structure welcomes the bindinf of another.

(d). One of the coordiantion sites of oxygen are bound by nitrogen of histidine amino acid. It helps in the movement of iron helix of the subunit.

(e). Nitrogen atom on the histidine amino acid is directly interacting with the iron atom.

f). No, because, change in aminoacids causes change in protein function, as each protein has unique sequence of amino acid. The required conformational changes may not be brought about by replacement of histidine with leucine.

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