Q. Hemoglobin is a tetrameric protein with two alpha and two beta polypeptide subunits. The structures of the alpha and beta subunits are remarkably similar to that of myoglobin. Myoglobin is also a heme containing protein that binds oxygen that has a structure that is similar to that of hemoglobin. However at a number of positions, hydrophilic residues in myoglobin have been replaced by hydrophobic residues in hemoglobin on the outside of the individual subunits.
a. How can this observation be reconciled with the generaliztion that hydrophobic residues fold into the interior of proteins?
b. In this regard, what can you say about the nature of the interactions that determine the quaternary structure of hemoglobin?