|MadSci Network: Cell Biology|
I'm not sure where you get the idea that one protein is hydrophilic and one hydrophobic. Both are quite soluble proteins and therefore predominately, in relative terms, hydrophilic. Both certainly have a number of what would normally be considered hydrophobic amino acids. Hemoglobin has a slightly higher percentage of these, but this is because it is an a2b2 tetramer whereas myoglobin is a monomer. Thus the entire surface of myoglobin is in contact with water and must therefore be, again in relative terms, hydrophilic. In contrast, the tetrameric structure of hemoglobin means that a significant amount of protein surface area is in contact not with water but with some other part of the tetrameric protein. Protein-protein contacts can be formed either from hydrophobic/hydrophobic interactions or hydrophilic/hydrophilic, rarely from a mixture. Most such protein-protein interactions are relatively hydrophobic. Simple consideration of the geometry will show that a higher percentage of surface amino acids on hemoglobin will be hydrophobic compared to myoglobin even though their overall structures are quite similar. If this doesn't answer your question or doesn't make sense, I'll try again.
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