most common amino acid?

Bernard Murray, PhD spam at
Fri Nov 19 21:38:14 EST 1999

In article <3835E08B.ECE43A14 at>, "Andrea Beckel-Mitchener, PhD"
<amitch at> wrote:

> Does anyone know which amino acid is found in the most abundance in
> proteins?  A good guess might be leucine due to the fact that it is
> coded for by 6 codons in the genetic code, however, this would assume
> that a gene's sequence is completely random.  Any other notions?

Do you mean;
a) The most abundant in the cell? (so dependent upon expression levels)
b) The most abundant in proteins?

If it is the latter I calculated the relative abundance in all
sequences in SwissProt release 36 (relative to W) as follows;
A  6.1
C  1.3
D  4.3
E  5.1
F  3.3
G  5.5
H  1.8
I  4.7
K  4.8
L  7.6
M  1.9
N  3.6
P  4.0
Q  3.2
R  4.1
S  5.8
T  4.6
V  5.3
W  1.0
Y  2.6

   So Leucine does indeed top the table.  You can see that many
assumptions have been made but at least you have real (??) numbers.

Bernard P. Murray, PhD
bpmurray at cgl . ucsf . edu
Department of Cellular & Molecular Pharmacology, UCSF

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