Why is proline frequently encountered at the places in the myoglobin and hemoglobin molecules where the polypeptide chain turns a corner?
A mutation that changes an alanine residue in a protein to an T isoleusine leads to a loss of activity. Activity is regained when a further mutation at the same site changes the Ile to a aly. Why?
Justify the following observations:
a. Ser can be replaced with the least effect on protein structure and function.
b. Replacement of Trp causes the greatest effect on protein structure and function.
c. Replacement of such as lys to Arg and Leu to Ile usually have very little effect on protein structure and function.