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Amino Acids
- 20 amino acids
- All amino acids have the same structure:
- Hydrogen
- Carboxylic Acid Group
- Amino Group
- Side Chain (R group)
- Each amino acid can be named in three ways:
- The full name
- A three letter identifier
- A single letter identifier
- 10 amino acids can be acquired through diet, but the rest need to be synthesized by our body
F H I K L M R T V W
Amino Acid Groups
- Amino acid composition drastically impacts protein function and characteristics
- Site directed mutagenesis: key amino acids are replaced with other amino acids. This can eliminate protein function, alter structure, or lead to protein unfolding
- Some key amino acids:
- Alanine: Single methyl group side chain. Used to virtually delete amino acids during site directed mutagenesis
- Proline: Side chain forms a ring connected to the amino group of the backbone. Much more rigid than other amino acids and is often found in turns and the beginning of alpha helices in proteins
- Tryptophan: Aromatic side chain. Is fluorescent and absorbs UV light (280nm), allowing proteins to be monitored
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A globular protein has a natural occurring mutation from Gln to Leu (Gln27Leu). If you wanted to recreate this mutation synthetically using a different amino acid substitution, what amino acid would have the most similar outcome?
a) Gln27Asn
b) Gln27Val
c) Gln27Glu
d) Gln27Ala
b) Valine has the same side chain as Leucine but is one carbon shorter. this will have the highest probability of behaving like the Gln27Leu mutation.
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A protein containing a key Glutamate (Glu133) residue in its active site is mutated as follows: E133A. What will happen to the overall activity of the protein?
E133A indicates that the glutamate residue at position 133 has been mutated to alanine. As you know alanine has the smallest side chain (a methyl group) and does not have any charged properties. Glutamate, on the other hand, has a carboxylic acid group that is negatively charged at physiological pH. Since Glu is a key amino acid, it must be involved in protein activity. Mutations to alanine are known to be a virtual deletion of the replaced amino acid so the protein will lose activity with the loss of Glu133.