Myoglobin and Haemoglobin?

Question

Given the extent to which tertiary structure is thought to depend on primary structure, how can a relatively hydrophobic ploypeptide such as the α or β subunit of haemoglobin have a tertiary structure very much like that of the relatively hydrophillic myoglobin?

Answer 1

good question. But in this case, similarity in tertiary structure is not the only way two proteins can have similar functions. The heme molecule is still what's responsible for binding oxygen. There are differences in the oxygen binding affinities of myoglobin and hemoglobin. And hemoglobin has allosteric properties. Further the dissociate curve for hemoglobin is sigmoidal whereas it is hyperbolic for myoglobin.

Answer 2

The interaction sites are almost identical. The rest of the protein is quite different, but the regions responsible for tertiary structure are not