NH2terminal

NH2terminal, often written as N‑terminal, designates the start of a polypeptide chain that bears a free amine (‑NH₂) group. During ribosomal protein synthesis the initiating methionine provides this primary amine, which may later be removed or chemically altered. The NH₂‑terminal region is distinguished from the carboxyl‑terminal (C‑terminal) end, which terminates in a free carbonyl (‑COOH) group.

The chemical nature of the NH₂‑terminal residue influences protein folding, stability, cellular localization, and interaction with other molecules. Post‑translational modifications frequently target this end; common examples include N‑acetylation, myristoylation, and ubiquitination, each altering the protein’s function or half‑life. In eukaryotes, N‑acetylation is one of the most prevalent modifications, occurring co‑translationally and affecting up to 80 % of cytosolic proteins.

Analytical techniques such as Edman degradation and mass spectrometry exploit the NH₂‑terminal amino group to sequence proteins or identify modifications. Mutations that alter the NH₂‑terminal amino acid can have pathogenic consequences, exemplified by certain hereditary diseases where loss of a signal peptide impedes proper protein trafficking.

In biotechnology, engineered NH₂‑terminal tags (e.g., His‑, FLAG‑, or HA‑tags) facilitate purification and detection of recombinant proteins. Understanding the properties of the NH₂‑terminal region remains essential for elucidating protein function, regulation, and design of therapeutic agents.