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Substitution preferences:
All protein types:
| Favoured | Phe ( 3) | Trp ( 2) | His ( 2) | |||||
| Disfavoured | Met (-1) | Leu (-1) | Gln (-1) | Val (-1) | Ile (-1) | Ala (-2) | Lys (-2) | Cys (-2) |
| Glu (-2) | Ser (-2) | Arg (-2) | Thr (-2) | Asn (-2) | Asp (-3) | Pro (-3) | Gly (-3) | |
| Favoured | Trp ( 2) | Phe ( 2) | His ( 1) | |||||
| Neutral | Leu ( 0) | Cys ( 0) | Val ( 0) | Ile ( 0) | Met ( 0) | |||
| Disfavoured | Ala (-1) | Asn (-1) | Glu (-1) | Pro (-1) | Gln (-1) | Arg (-1) | Ser (-1) | Thr (-1) |
| Lys (-1) | Asp (-2) | Gly (-2) |
| Favoured | Phe ( 2) | Trp ( 1) | ||||||
| Neutral | Val ( 0) | Ile ( 0) | His ( 0) | Arg ( 0) | ||||
| Disfavoured | Ala (-1) | Glu (-1) | Lys (-1) | Met (-1) | Leu (-1) | Asn (-1) | Pro (-1) | Gln (-1) |
| Ser (-1) | Thr (-1) | Gly (-2) | Asp (-2) | Cys (-4) |
| Favoured | His ( 6) | Cys ( 3) | Phe ( 2) | Lys ( 1) | ||||
| Neutral | Gln ( 0) | Ser ( 0) | ||||||
| Disfavoured | Arg (-1) | Asn (-1) | Asp (-2) | Leu (-2) | Thr (-3) | Trp (-3) | Ala (-3) | Met (-3) |
| Ile (-4) | Val (-4) | Pro (-5) | Glu (-5) | Gly (-5) |
Substitutions: As Tyrosine is an aromatic, partially hydrophobic, amino acid, it prefers substitution with other amino acids of the same type (see above). It particularly prefers to exchange with Phenylalanine, which differs only in that it lacks the hydroxyl group in the ortho position on the benzene ring.
Role in structure: Being partially hydrophobic, Tyrosine prefers to be buried in protein hydrophobic cores. The aromatic side chain can also mean that Tyrosine is involved in stacking interactions with other aromatic side-chains.
Role in function: Unlike the very similar Phenylalanine, Tyrosine contains a reactive hydroxyl group, thus making it much more likely to be involved in interactions with non protein atoms.
Like other aromatic amino acids, Tyrosine can be involved in interactions with non-protein ligands that themselves contain aromatic groups via stacking interactions.
Like other aromatic amino acids, Tyrosine can be involved in interactions with non-protein ligands that themselves contain aromatic groups via stacking interactions. Tyrosine and other aromatic amino acids can be involved in binding to poly-proline containing peptides, for example, in SH3 or WW domains.
A common role for Tyrosines (and Serines and Threonines) within intracellular proteins is phosphorylation. Protein kinases frequently attach phosphates to Tyrosines in order to fascilitate the signal transduction process. Note that in this context, Tyrosine will rarely substitute for Serine or Threonine, since the enzymes that catalyse the reactions (i.e. the protein kinases) are highly specific (i.e. Tyrosine kinases generally do not work on Serines/Threonines and vice versa).