N-terminus

Definition

The N-terminus, or amino-terminus, refers to the end of a polypeptide or protein chain that contains a free amino group. It is one of the two ends of a protein molecule and is an important structural feature that helps determine the overall folding and function of the protein.

5 Must Know Facts For Your Next Test

1. The N-terminus is the first amino acid in a polypeptide chain, with a free amino group (-NH2) at the end.
2. The N-terminus plays a crucial role in protein folding and stability, as it can interact with other parts of the protein structure.
3. The Edman degradation, a method of peptide sequencing, relies on the N-terminus to identify the amino acid sequence of a protein.
4. The N-terminus can undergo post-translational modifications, such as acetylation or myristoylation, which can alter the protein's function or localization.
5. Identifying the N-terminus is important in proteomics research, as it can provide information about the protein's origin, processing, and potential function.

Review Questions

• Explain the significance of the N-terminus in the context of peptides and proteins.
  • The N-terminus of a polypeptide or protein chain is an important structural feature that plays a crucial role in determining the overall folding and function of the protein. As the first amino acid in the sequence, the N-terminus contains a free amino group (-NH2) that can interact with other parts of the protein structure, contributing to its stability and conformation. Additionally, the N-terminus is a key starting point for various analytical techniques, such as the Edman degradation, which is used to determine the amino acid sequence of a protein by sequentially removing and identifying the N-terminal amino acids.
• Describe how the N-terminus is utilized in the Edman degradation method of peptide sequencing.
  • The Edman degradation is a technique used to determine the amino acid sequence of a polypeptide or protein by sequentially removing and identifying the N-terminal amino acids. This method relies on the presence of the free amino group at the N-terminus of the protein. During the Edman degradation, the N-terminal amino acid is selectively labeled and cleaved from the chain, allowing for its identification. This process is repeated, progressively revealing the amino acid sequence of the protein from the N-terminus to the C-terminus. The information obtained from the Edman degradation is crucial for understanding the structure and function of the protein.
• Analyze the potential impact of post-translational modifications on the N-terminus and how this can influence protein function and localization.
  • The N-terminus of a protein can undergo various post-translational modifications, such as acetylation or myristoylation, which can significantly impact the protein's function and localization within the cell. These modifications can alter the chemical properties of the N-terminus, affecting its interactions with other parts of the protein structure or with external factors. For example, N-terminal acetylation can stabilize the protein and prevent degradation, while myristoylation can promote membrane association and subcellular targeting. Understanding the role of the N-terminus and the potential effects of post-translational modifications is crucial for elucidating the complex regulatory mechanisms that govern protein function and cellular processes.

Related terms

Polypeptide:

A polymer consisting of amino acids linked by peptide bonds, forming the basic structural unit of proteins.

Peptide Bond:

A covalent bond that links the carboxyl group of one amino acid to the amino group of another, forming the backbone of a polypeptide chain.

Protein Folding: The process by which a protein structure assumes its functional 3D shape from its primary amino acid sequence.