Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 13

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 part (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 part (b). In the deoxy form, the space between the iron atoms is too small to hold O 7 , 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 which replaced aspartic acid 85 by a lysine residue