Question

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 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? (1 point)
(b) What is the role of amino acid 52? (1 point)
(c) What do you conclude from the double mutation G46V+H52G?

Answer 1

Receptor binding hormones

Step-by-step explanation:

(A) When the amino acid A at position 48 is mutated to either V or R, binding does not happen. This indicates that the amino acid A at position 48 is vital for the binding of growth hormone to the receptor.

(B) When the amino acid H at position 52 is mutated to either G or D, binding does not happen. This indicates that the amino acid H at position 52 is vital for the binding of growth hormone to the receptor.

(C) When the amino acid G at position 46 alone is mutated to V, binding happens. When the amino acid H at position 52 alone is mutated to G, no binding happens. However, when double mutation G46V+H52G happens, there is no binding. This shows amino acid 46 is not affecting the binding but amino acid 52 is crucial for the binding.