Primary structure of proteins

Rolf Apweiler apweiler at
Fri Sep 6 03:13:32 EST 1996

In article <32281FA9.484D at>, Andres Kreegipuu <andres at> writes:
>I am looking for information about the average occurence frecuency of
>the 20 natural amino acids in proteins. Are these data available
>Andres Kreegipuu
Here some statistics from the release notes of SWISS-PROT release 33 
(52205 protein sequence entries):

                         APPENDIX A: SOME STATISTICS

   A.1  Amino acid composition

        A.1.1  Composition in percent for the complete data bank

   Ala (A) 7.54   Gln (Q) 4.02   Leu (L) 9.31   Ser (S) 7.19
   Arg (R) 5.15   Glu (E) 6.31   Lys (K) 5.94   Thr (T) 5.76
   Asn (N) 4.54   Gly (G) 6.86   Met (M) 2.36   Trp (W) 1.26
   Asp (D) 5.29   His (H) 2.23   Phe (F) 4.06   Tyr (Y) 3.21
   Cys (C) 1.70   Ile (I) 5.72   Pro (P) 4.91   Val (V) 6.52

   Asx (B) 0.001  Glx (Z) 0.001  Xaa (X) 0.02

        A.1.2  Classification of the amino acids by their frequency

   Leu, Ala, Ser, Gly, Val, Glu, Lys, Thr, Ile, Asp, Arg, Pro, Asn, Phe,
   Gln, Tyr, Met, His, Cys, Trp

I hope that will help.


Rolf Apweiler

(SWISS-PROT Coordinator)

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