Question

Identify the polar amino acids, the aromatic amino acids, and the sulfur- containing amino acids, given a peptide with the following amino acid sequence: Val-Met-Ser-Ile-Phe-Arg-Cys-Tyr-Leu

Short answer

Polar: Ser, Arg; Aromatic: Phe, Tyr; Sulfur: Met, Cys

Step-by-step solution

Identify Polar Amino Acids

Polar amino acids have side chains that can form hydrogen bonds with water. In the given sequence, these are Ser (Serine) and Arg (Arginine).

Identify Aromatic Amino Acids

Aromatic amino acids have a ring structure in their side chain. In the given sequence, these are Phe (Phenylalanine) and Tyr (Tyrosine).

Identify Sulfur-Containing Amino Acids

Sulfur-containing amino acids have sulfur in their side chain. In the given sequence, these are Met (Methionine) and Cys (Cysteine).

Summarize Findings

List the identified polar, aromatic, and sulfur-containing amino acids from the given peptide sequence.

Key concepts

Polar Amino Acids

Polar amino acids have side chains that can interact with water through hydrogen bonds. This property makes them hydrophilic and essential for many biological processes. In the peptide sequence provided, the polar amino acids identified are Serine (Ser) and Arginine (Arg).

- **Serine (Ser)**: Serine’s side chain includes a hydroxyl group (-OH) which can form hydrogen bonds easily. This makes it very soluble in water. It’s often involved in catalytic functions of enzymes.
- **Arginine (Arg)**: Arginine has a complex side chain with a guanidinium group that can form multiple hydrogen bonds. It is positively charged at physiological pH, which makes it very hydrophilic. Arginine is crucial in protein-protein interactions and enzyme binding sites.

Aromatic Amino Acids

Aromatic amino acids are characterized by the presence of an aromatic ring in their side chain, which contributes to the protein’s structure and can participate in hydrophobic interactions. The aromatic amino acids in the given sequence are Phenylalanine (Phe) and Tyrosine (Tyr).

- **Phenylalanine (Phe)**: This amino acid has a benzyl side chain, making it hydrophobic. It is important in maintaining the protein’s structural integrity through hydrophobic interactions.
- **Tyrosine (Tyr)**: Tyrosine has a phenol group in its side chain, which can form hydrogen bonds but is also aromatic, allowing it to interact hydrophobically. Tyrosine also plays a role in signal transduction due to its ability to be phosphorylated.

Sulfur-Containing Amino Acids

Sulfur-containing amino acids are unique due to the sulfur atoms in their side chains, which are important for protein function and structure. The sulfur-containing amino acids in the sequence are Methionine (Met) and Cysteine (Cys).

- **Methionine (Met)**: Methionine has a thioether group in its side chain. It is often used as the start codon in protein synthesis and plays a key role in methylation processes.
- **Cysteine (Cys)**: Cysteine contains a thiol group (-SH), which is reactive and can form disulfide bonds. Disulfide bonds are crucial in stabilizing the tertiary and quaternary structures of proteins.