What are chemical modifications at N terminal end

Chemical modifications at the N-terminal end of proteins involve covalent alterations to the terminal amino acid residue or residues. Here are some common chemical modifications that can occur at the N-terminal end:

1. Acetylation:

   • N-terminal acetylation involves the addition of an acetyl group (-COCH3) to the amino group (-NH2) of the N-terminal amino acid residue.
   • This modification is typically catalyzed by N-terminal acetyltransferases (NATs) and is prevalent in eukaryotic proteins.
   • N-terminal acetylation can influence protein stability, subcellular localization, and interactions with other molecules.

2. Methylation:

   • N-terminal methylation involves the addition of methyl groups (-CH3) to the amino group (-NH2) of the N-terminal amino acid residue.
   • This modification can occur enzymatically or through chemical reactions with methylating agents.
   • N-terminal methylation can affect protein-protein interactions, transcriptional regulation, and cellular signaling pathways.

3. Cyclization:

   • N-terminal cyclization involves the formation of a cyclic structure at the N-terminal amino acid residue through covalent bond formation.
   • This modification can occur through various chemical reactions, including cyclization of the amino group with the side chain of a nearby amino acid residue.
   • N-terminal cyclization can alter protein stability, conformation, and enzymatic activity.

4. Amidation:

   • N-terminal amidation involves the conversion of the terminal amino group (-NH2) of the N-terminal amino acid into an amide group (-CONH2).
   • This modification occurs through enzymatic processes involving amidating enzymes, resulting in the loss of the amino group and the formation of an amide bond.
   • N-terminal amidation can enhance the stability and biological activity of peptides and proteins.

5. Blocking:

   • N-terminal blocking involves the addition of chemical groups or molecules to the amino group (-NH2) of the N-terminal amino acid residue, preventing further modifications or interactions.
   • Common blocking agents include acetyl groups, formyl groups, or other chemical moieties that can mask the amino group.
   • N-terminal blocking can be used for chemical protection or to control the reactivity of the N-terminal end in specific applications.

These are some examples of chemical modifications that can occur at the N-terminal end of proteins. Each modification can have distinct effects on protein structure, function, stability, and interactions, influencing various cellular processes and physiological functions.