Question

Why does E6V hemoglobin polymerize?

Answer 1

E6V is the mutation seen in the sickle cell anaemia where E (Glutamate) amino acid at the sixth position of Beta- a chain of Haemoglobin subunit to V (Valine).  

HbA is the normal form of Haemoglobin and HbS is the Sickle cell form of Haemoglobin. The oxy form is right so there is no problem in the oxygen-carrying by Haemoglobin. The usual function is still carried out. But there is a gain of function mutation here wherein the deoxy state, the beta subunit has hydrophilic patches exposed due to presence of valine in the place of glutamate which leads to form of a polymer of glued hydrophobic patches of a subunit of one HbS to another and thus leading to polymerisation. The change from oxy to the deoxy state of Hb occurs within femtoseconds. Thus, at higher altitudes when the oxygen level is less, there is more no in deoxy state Hb and more no of polymerised forms which can block the vessels and stop the blood flow which would otherwise carry O2 and nutrients. The hydrophobicity of valine i.e. mutant leads to polymerisation of mutant Hb or E6V mutation Hb.

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