asparagineresidu

Asparagine residue, abbreviated Asn or N, refers to the amino acid asparagine when incorporated into a protein. Its side chain is a carboxamide (–CH2–CONH2). The residue is polar and uncharged at physiological pH and can participate in hydrogen bonding with surrounding groups.

In protein structure, Asn residues often reside on surfaces and can stabilize folds through hydrogen bonding, or participate in catalytic networks in enzymes. The amide side chain can act as both hydrogen-bond donor and acceptor.

N-linked glycosylation attaches an oligosaccharide to the amide nitrogen of the Asn side chain within the consensus motif Asn-X-Ser/Thr (N-X-S/T, X not Pro). This modification is common in secreted and membrane proteins and contributes to folding, stability, and trafficking.

Asparagine can undergo non-enzymatic deamidation to form aspartate or isoaspartate, potentially changing charge and conformation. Deamidation increases with time and temperature and is a factor in protein aging. Repair is carried out by protein L-isoaspartyl methyltransferase (PIMT).

In biotechnology and medicine, the pattern of Asn-linked glycosylation and the susceptibility of Asn residues to deamidation influence the behavior of therapeutic proteins and the interpretation of protein function in research.