Question

A.Human Hemoglobin does not bind Bicarbonate. Twelve amino acid substitutions had to be made in human hemoglobin in order to force human hemoglobin to bind bicarbonate at the a1-B1 subunit interface. Yet, only three amino acids interact with the bicarbonate ion. Wht might be the role of the other 9 ammino acids in facilitating binding?

B. The plausible bicarbonate binding site is at the interface between the crocodile hemoglobin a1-B1 subunit, where the two subunits slide with respect to each other during the R to T transitions. Three amino acid residues are predicted to interact with bicarbonate, the phenolate anion of Tyr41 of the Bsubunit, the E-amino group of Lys38 of the B subunit, and the phenolate anion of Tyr 41 of the a-subunit. Which set of molecular interactions will govern the association between bicarbonate and crocodile hemoglobin?

Answer 1

A) Its function would be to stabilize the molecule once it begins to interact the bicarbonate ion with the other three amino acids.

B) CO₂ is converted to protons and bicarbonate ions as follows: CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃^-, H+ is an allosteric inhibitor that specifically binds the deoxy or T state of hemoglobin, shifting the equilibrium from the R state to the T state. This is the pH Bohr Effect. The interactions that govern the association between cocodrile hemoglobin and bicarbonate are hydrogen bonds and Van der Waals forces .