If the histidine on the E helix $($His E$7)$ that coordinates the O $2$ that binds to the heme iron in hemoglobin is mutated to an alanine, what effect would be most likely?

Oxygen binding affinity would increase, since the alanine residue would form strong interaction with the oxygen molecule.

Oxygen binding would take place on the other face of the heme molecule, where the "proximal" histidine would be able to interact with the oxygen.

Oxygen binding would not cause the movement of the F helix, since the alanine at E$7$ cannot coordinate oxygen.

Oxygen binding would cause hemoglobin polymers to form, due to the introduction of a hydrophobic patch by the addition of this alanine.