N terminal

N-Terminal or Amino-Terminal refers to the start of a protein or polypeptide referring to the free amino acid end. Proteins are directional, meaning they have an end to end sequence of amino acids that is significant to their structure and function. The N-Terminal is the part of the protein that is synthesized first, and it is often a critical component of protein function.

Structure and Function

The N-Terminal is named for the amine group (NH2) that is free when the amino acid is incorporated into a peptide. This end of the protein is often modified post-translationally, meaning after the protein has been synthesized by the ribosome. These modifications can include the addition of other functional groups like phosphate, acetyl, or methyl groups, or even larger structures like carbohydrates in a process called glycosylation.

These modifications can have significant effects on the protein's function, including its ability to interact with other proteins or molecules, its stability and lifespan within the cell, and its localization within the cell or body.

N-Terminal Sequencing

N-terminal sequencing is a method used in protein sequencing to identify the amino acid sequence of a protein's N-terminal end. This can be useful in identifying unknown proteins or confirming the identity of a known protein. The most common method for N-terminal sequencing is the Edman degradation, which sequentially removes one amino acid at a time from the N-terminal end of the protein.

N-Terminal Tags

In molecular biology, it is common to add an "N-terminal tag" to a protein of interest. This tag, which is a short sequence of amino acids, is added to the N-terminal end of the protein during the process of DNA cloning. The tag can then be used to purify the protein from a mixture, to visualize the protein using immunofluorescence, or to study the protein's function in a controlled way.

See Also

• C-Terminal
• Protein sequencing
• Post-translational modification
• Edman degradation