Assume that a new oxygen-transport protein has been discovered in certain invertebrate animals. X-ray diffraction of the

Question:

Assume that a new oxygen-transport protein has been discovered in certain invertebrate animals. X-ray diffraction of the deoxy protein reveals that it has the dimeric structure shown here in panel (a) with a salt bridge between residues histidine 13 and aspartic acid 85. The two monomers interact by salt bridges between the C- and N-termini. The O2-binding site lies between the two iron atoms shown, which are rigidly linked to helices A and C (see panel (b)). In the deoxy form, the space between the iron atoms is too small to hold O2, and so the Fe atoms must be forced apart when O2 is bound. Answer the following questions, explaining your answer in each case in terms of the structure shown below.
(a) Is this molecule likely to show cooperative oxygen binding?
(b) Is this molecule likely to exhibit a Bohr effect?
(c) Predict the likely effect of a mutation that replaced aspartic acid 85 by a lysine residue.