Question

Histone proteins are rich in which of the following basic amino acids?

• A. Arginine and Lysine
• B. Alanine and Glycine
• C. Histidine and Serine
• D. Tyrosine and Cysteine

Answer 1

The correct option is A

Arginine and Lysine

The correct option is A.

Explanations of correct option:

Option A:

1. Histones are positively charged proteins that help in the coiling of DNA.
2. They help in DNA regulation as well.
3. The basic amino acids that make up the histone proteins are Arginine and Lysine.
4. Arginine is a hydrophilic (water-loving) basic amino acid.
5. Lysine is the most basic amino acid.
6. They are basic as they have a positive charge on their side chains at the physiological pH.

Explanations of incorrect options:

Option B:

1. Glycine is the most simple amino acid as its side chain has only a single H-atom.
2. Alanine is also a non-polar amino acid but it has a hydrophobic side chain.
3. Alanine and Glycine are not present in Histone proteins.

Option C:

1. Histidine is also a positively charged basic amino acid.
2. Histidine is the amino acid with the least basic character.
3. Serine is also a polar (dipole moment due to a charge) amino acid but it does not have a charge.
4. Histidine and Serine are not present in Histone proteins.

Option D:

1. Tyrosine is a hydrophobic (water-hating) amino acid. Tyrosine is non-polar and has an aromatic group (conjugated planar rings) in its side chain.
2. Cysteine is a polar amino acid but does not have a charge. Cysteine is hydrophobic.
3. Cysteine has a sulfur group in its side chain.
4. Tyrosine and Cysteine are not present in Histone proteins.

Final answer: Histone proteins are rich in basic amino acids Arginine and Lysine.