Glutamate

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Standard codons for E : GAA GAG

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

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

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

Membrane proteins:
Favoured Asp ( 8) Gln ( 7) Gly ( 3) His ( 2) Arg ( 2) Asn ( 1) Lys ( 1)
Neutral Ala ( 0) Ser ( 0)
Disfavoured Thr (-1) Val (-2) Trp (-3) Cys (-3) Pro (-3) Met (-3) Ile (-4) Leu (-5)
Tyr (-5) Phe (-6)

Substitutions: Glutamate (or Glutamic acid) is a negatively charged, polar amino acid. It thus most prefers to substitute for the other negatively charged (and very similar) amino acid Aspartate, though it can also substitute with other polar amino acids, in particular Glutamine, which differs only in that it contains an amino group in place of one of the oxygens found in Glutamate (and thus also lacks a negative charge).

Role in structure: Being charged and polar, Glutamates, prefer generally to be on the surface of proteins, exposed to an aqueous environment. When buried within the protein Glutamates (and Aspartates) are frequently involved in salt-bridges, where they pair with a positively charged amino acid to create stabilising hydrogen bonds, that can be important for protein stability.

Role in function: Glutamates are quite frequently involved in protein active or binding sites. The negative charge means that they can interact with positively charged non-protein atoms, such as cations like zinc. In certain cases, they can also perform a similar role to Aspartate, in the catalytic site of proteins such as proteases or lipases.

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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..