Tyrosine

Atom Label Key

Naming Convention for α-amino acids

The Organic acid carbon is labled the acid.
Each carbon afterwards is labeled in order by the greek alphabet
α, β, γ, δ, ε, etc.
Every atom is labeled by element type and then its position ie. the alpha carbon is CA; the beta carbon is CB

Atom Label	Description

C	Main chain Carbon of amide/acid
CA	Main chain α carbon
N	Main chain nitrogen of amide/amine
O	Main chain Oxygen of amide/acid
H	Main chain hydrogen of amide
HA	Main chain hydrogen of on the α carbon
CB	β Carbon, first carbon of the sidechain
HB?	Hydrogen on the β Carbon. '?' is a number 1,2 or 3
OG	Oxygen on the β Carbon.
CG?	γ Carbon. - the '?' if present is a number 1 or 2

The results are shown. The H from the -OH group on C6 is now on the amino acid side chain. The phosphate group has been transferred to the alcohol carbon of glucose and ADP is the other product.

Tyrosine

Name

3 Letter

1 Letter

Tyrosine

TYR

protonated (acid form and neutral)
This is the dominant form
Tyrosine

unprotonated (base form and negative)
There is very little of this under normal conditions

Drawn as if part of protein to emphasize the sidechain properties

The "Sidechain Polarity" button draws an an envelope around the sidechain that is colored by charge according to the scale above.

pK_R in H₂O= 10.1

Free amino acid mass = 181 g/M

Probability of being found in a:

α-Helix

β-Sheet

β-Turn

30%

85%

75%

Special Attributes

Large bulky aromatic amino acid side chain.

Due to the aromatic character AND the terminal hydroxyl group this side chain has a large light absorption property at 280nm.

Considerably more polar than pheylalanine. The hydroxyl group is an OH hydrogen bond donor and acceptor.

The -OH group under normal conditions has a pK of about 10 (note this is considerably lower than that for SER and THR - this is due to the aromatic character of the ring). In rare cases, the pK can be shifted by a large degree in some cases such that the ionized form can be seen in some proteins.

It can also be used in some cases as a metal ligand. If the metal is Fe or Mn then the protein will have a purple color because of the metal - tyrosine charge transfer.

In the demonstration below, the TYR is in a section of random coil and is partially buried in the protein with the hydroxyl group peeking out into water.

In the demonstration below you may "left click and drag" to rotate the molecule "SHIFT left click and drag (up or down)" to make smaller or bigger
Click on the white squares in succession to turn or/off identifying features. Some text describing the issues is in the lower right text box

	Atom Label Description
	Click an atom to diplay it's identity here
	Messages about the currently highlighted features

Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/