Valine can be a homologous substitution for isoleucine in a protein sequence

047. Which one of the following can be a homologous substitution for isoleucine in a protein sequence?

1. Methionine

2. Aspartic acid

3. Valine

4. Arginine

Answer

3. Valine

Reference:

Harper 26^th Edition Page 15

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Discussion

Homologous substitutions are those which don’t affect the function. Valine is an amino acid with aliphatic side chain and isoleucine also has aliphatic side chain

Explanation

1. Methionine is a sulphur containing aminoacid and will not be a homologous substitution for isoleucine

2. Aspartic acid has a acidic side chain and will not be a homologous substitution for isoleucine

3. Valine has aliphatic side chain and will be a homologous substitution for isoleucine

4. Arginine has a basic side chain and will not be a homologous substitution for isoleucine

Comments

Some time back we used to have questions directly from the Classification of Amino Acids such as “The basic amino acid is” All of the following has aliphatic side chains except” Now questions gyrating around the same topic are asked in an indirect way.

Tips

Hemoglobinopathies as well as classification of proteins are important topics. For an overview about the Hemoglobinopathies, refer to Q.No 30 in RxPG AIPG 2003 book