A very new Hemoglobin variant, called Hb simplex, has just been identified in patients with hypoxia (i.e. patients for whom the oxygenation of organs is not properly accomplished). However, this variant is able to bind dioxygen with a Kd which is significantly lower to that of Hemoglobin from normal patients. This effect has been associated with the substitution of a Lys by a Met at two distinct sites of the b subunit of Hemoglobin : one site close to the N-terminus, and the other site close to the C-terminus of the polypeptide chain. Most importantly, these 2 sites are known to be involved in the maintain of the physical interactions between the subunits a and b in Hemoglobin. 1) The aforementioned Hb simplex mutations lead to a loss of physical interactions between the subunits a and b. What type(s) of chemical bonds between the 2 subunits (i.e. covalent, electrostatic, ion-dipole, dipole-dipole, van der waals) would you hypothesize to be affected by these mutations? explain. 2) Would you expect to find the Hb simplex more in the form of a tetramer, a dimer, or a monomer? Why? (Hint: a subunits do not interact directly between themselves in the Hemoglobin normal tetrameric structure). 3) Considering these new structural attributes, would you expect the Hb simplex to show an allosteric behavior or not? also, how these changes relate to the hypoxic state of the patient? Explain.

A very new Hemoglobin variant, called Hb simplex, has just been identified in patients with hypoxia (i.e. patients for whom the oxygenation of organs is not properly accomplished). However, this variant is able to bind dioxygen with a Kd which is significantly lower to that of Hemoglobin from normal patients. This effect has been associated with the substitution of a Lys by a Met at two distinct sites of the b subunit of Hemoglobin : one site close to the N-terminus, and the other site close to the C-terminus of the polypeptide chain. Most importantly, these 2 sites are known to be involved in the maintain of the physical interactions between the subunits a and b in Hemoglobin.

1) The aforementioned Hb simplex mutations lead to a loss of physical interactions between the subunits a and b. What type(s) of chemical bonds between the 2 subunits (i.e. covalent, electrostatic, ion-dipole, dipole-dipole, van der waals) would you hypothesize to be affected by these mutations? explain.

2) Would you expect to find the Hb simplex more in the form of a tetramer, a dimer, or a monomer? Why? (Hint: a subunits do not interact directly between themselves in the Hemoglobin normal tetrameric structure).

3) Considering these new structural attributes, would you expect the Hb simplex to show an allosteric behavior or not? also, how these changes relate to the hypoxic state of the patient? Explain.