N-terminal

N-terminal
Illustration of a protein with the N-terminal highlighted
Identifiers
Symbol	?

The N-terminal (or amino-terminal) of a protein is the end of the protein chain that contains a free amine group (-NH₂). It is the starting point of protein synthesis and plays a crucial role in the function and stability of proteins. Understanding the N-terminal is essential for comprehending protein structure, function, and the mechanisms of protein synthesis.

Structure and Function

The N-terminal is the first part of a protein to be synthesized during translation on the ribosome. It is encoded by the 5' end of the mRNA and emerges from the ribosome first. The N-terminal can influence the protein's folding, stability, and localization within the cell.

Amino Acid Sequence

The sequence of amino acids at the N-terminal can determine the targeting of the protein to specific cellular compartments. For example, proteins destined for the endoplasmic reticulum often have a signal peptide at their N-terminal.

Post-Translational Modifications

The N-terminal can undergo various post-translational modifications such as acetylation, methylation, and ubiquitination. These modifications can affect the protein's function, interaction with other molecules, and degradation.

Role in Protein Degradation

The N-terminal rule is a concept in protein degradation that suggests the identity of the N-terminal amino acid can influence the half-life of a protein. Proteins with certain N-terminal residues are more rapidly degraded by the ubiquitin-proteasome system.

N-terminal Sequencing

N-terminal sequencing is a method used to determine the amino acid sequence at the N-terminal of a protein. This can be achieved through techniques such as Edman degradation.

Clinical Significance

Alterations in the N-terminal sequence or modifications can lead to diseases. For example, improper N-terminal acetylation has been linked to cancer and neurodegenerative diseases.

Also see

• C-terminal
• Protein structure
• Protein synthesis
• Post-translational modification
• Signal peptide

This diagram (which is interactive) of protein structure uses PCNA as an example. (PDB: 1AXC​)