NTerminal

Nterminal, sometimes spelled N-terminal, is a term used in molecular biology to designate the N-terminus of a polypeptide or protein—the end of the amino acid sequence that bears a free amino group. In standard notation, proteins are written from the N-terminus to the C-terminus, with the C-terminus at the opposite end. The N-terminus often features distinct chemical and functional properties that can influence protein localization, stability, and interactions.

In biological systems, the N-terminus is frequently subject to processing and modification. Many proteins begin with a methionine residue that may be removed by methionine aminopeptidase depending on context, and the exposed N-terminus can subsequently undergo acetylation or other modifications. The N-terminus can also contain targeting signals, such as signal peptides directing secretion or transit peptides directing import into mitochondria or chloroplasts. These features help determine protein maturation and cellular localization.

Analytically, identifying the N-terminus is important for understanding protein function and annotation. Techniques include Edman degradation, which sequentially identifies N-terminal residues, and mass spectrometry-based N-terminomics approaches that map start sites and processing events on a proteome-wide scale. N-terminal information supports genome annotation, proteomics, and studies of protein turnover and stability.

The term Nterminal may appear in literature as an alternate spelling of N-terminal or as part of product names, databases, or software that reference the N-terminus. In protein engineering, N-terminal tags and fusions are commonly used to aid purification, detection, or localization, illustrating the practical relevance of the N-terminus in research and biotechnology.