Asparagine

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Standard codons for N : AAC AAT

Substitution preferences:
All protein types:
Favoured Ser ( 1) His ( 1) Asp ( 1)
Neutral Thr ( 0) Glu ( 0) Lys ( 0) Gly ( 0) Gln ( 0) Arg ( 0)
Disfavoured Ala (-2) Met (-2) Tyr (-2) Pro (-2) Phe (-3) Val (-3) Ile (-3) Leu (-3)
Cys (-3) Trp (-4)

Intracellular proteins:
Favoured Asp ( 1)
Neutral Thr ( 0) Glu ( 0) Lys ( 0) Gly ( 0) His ( 0) Gln ( 0) Arg ( 0) Ser ( 0)
Disfavoured Ala (-1) Cys (-1) Pro (-1) Tyr (-1) Met (-1) Leu (-2) Val (-2) Trp (-2)
Phe (-2) Ile (-2)

Extracellular proteins:
Favoured Asp ( 1)
Neutral Ala ( 0) Glu ( 0) Thr ( 0) Gly ( 0) His ( 0) Lys ( 0) Pro ( 0) Gln ( 0)
Arg ( 0) Ser ( 0)
Disfavoured Met (-1) Ile (-1) Val (-1) Tyr (-1) Phe (-2) Leu (-2) Trp (-3) Cys (-6)

Membrane proteins:
Favoured Asp ( 6) Lys ( 5) Gln ( 3) His ( 3) Ser ( 2) Arg ( 2) Glu ( 1) Thr ( 1)
Disfavoured Ala (-1) Tyr (-1) Cys (-1) Pro (-2) Gly (-2) Met (-2) Trp (-3) Val (-3)
Ile (-3) Leu (-4) Phe (-4)

Substitutions: Asparagine is a polar amino acid. It thus most prefers to substitute for other polar residues, in particular Aspartate, which differs only in that it contains an oxygen in place of the amino group in Asparagine. It can also substitute with other polar amino acids.

Role in structure: Being polar, Asparagine prefers generally to be on the surface of proteins, exposed to an aqueous environment.

Role in function: Asparagines are quite frequently involved in protein active or binding sites. The polar side-chain is good for interactions with other polar or charged atoms.

Asparagine can play a similar role to Aspartate in some proteins. Probably the best example is found in certain Cysteine proteases, where it forms part of the Asn-His-Cys catalytic triad:

In this context, it is quite rare to see Asparagine exchange for Glutamine.

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Please cite: M.J. Betts, R.B. Russell. Amino acid properties and consequences of subsitutions.
In Bioinformatics for Geneticists, M.R. Barnes, I.C. Gray eds, Wiley, 2003..