In the growth hormone, the receptor binding domain was mapped from amino acids 48-60. In order to determine, which amino acids are involved in its binding to the receptor, the following mutations were performed and the binding assay results are listed below.

MUTATIONS BINDING ASSAY RESULTS
A48 V Yes
G46V No
A48R Yes
H52G Yes
G46R No
H52D No
G46V+H52G No
A48R + H52G No

a. What is the role of the amino acid 48?
b. What is the role of amino acid 52?
c. What do you conclude from the double mutation G46V+H52G?
d. What did you learn from the double mutation A48R+H52G?
e. Which amino acids are important in hormone binding to receptor?