N-Terminus

As the N- terminus or amino- terminus of that end of a protein or polypeptide refers to that in eukaryotes and archaea having an amino acid having a free amino group ( NH2). Proteins newly synthesized in bacteria, however, beginning with N- formyl methionine ( fMet ), in which the amino group is formylated.

Properties

The ribosome starts the protein at the N -terminus with a methionine as the first amino acid of the newly formed protein. The N-terminus is initially unmodified, while the carboxy group of the amino acid via a peptide bond with the NH2 group of the next amino acid is covalently linked.

The free amino group is the N -terminus of the name, but can be variously modified subsequently during and after the translation. Thus, the N-terminus is acetylated in eukaryotes often as part of a post-translational modification by a acetyl, or occasionally myristylated palmityliert. Specific N- terminal modifications include, for example cleaving of parts by proteolysis or subsequent attachment of amino acids as in the arginylation. By proteolysis of a protein are novel proteins may result from the C- terminal fragments, the N- terminal amino acid is no longer a methionine. With methionine aminopeptidase, the methionine at the N -terminus may be cleaved. The N-terminal amino acid may accelerate proteolytic degradation of a protein which will be described by the N -end rule.

Shortly after the N-terminus is often a signal sequence, such as the. For secretory or mitochondrial proteins in all eukaryotic cells and proteins to the plastid of plants

The opposite end of the molecule of any peptide is referred to as the carboxy -terminus ( short C -terminus ).