Q. 16.68 - An Introduction to General, Organic, and Biological Chemistry

Question

If glycine were replaced by alanine in a protein, how might the tertiary structure be affected? $(16.1,16.3)$

Step-by-Step Solution

Answer

1. Replacing the proteins glycine and alanine does not affect tertiary structure.  
2. The reason is that both amino acids are naturally non-polar.

Step 1: Introduction Protein and The functions of Tertiary structure

• Tertiary structure is the three-dimensional shape of a protein. 
• Tertiary structure contains the attractive and repulsive forces between the $R$ groups of amino acids in the polypeptide chain of a protein. 

Step 2: Given Information i) Glycine Structure

i) The structure of Glycine is

This structure contains a non-polar $R$ group. 

• Within the protein, there is a hydrophobic interaction between the two non-polar $R$ groups.
• In this tertiary structure, the non-polar $R$ groups separate to form a hydrophobic center within the protein molecule. 

Step 3: Given Information ii) Alanine structure

ii) The structure of alanine is 

In alanine, the $-{\mathrm{CH}}_3$ group is prepended instead of the $H$ atom.  

Step 4: Explanation The effect of Tertiary structure when glycine were replaced by alanine in a protein.

• When Alanine is used in place of glycine in proteins, but this does not affect tertiary structure because both amino acids are essentially non-polar.