Influence of genomic G+C content on average amino-acid composition of proteins from 59 bacterial species

Gene. 1997 Dec 31;205(1-2):309-16. doi: 10.1016/s0378-1119(97)00403-4.


The amino-acid composition of 23,490 proteins from 59 bacterial species was analyzed as a function of genomic G+C content. Observed amino-acid frequencies were compared with those expected from a neutral model assuming the absence of selection on average protein composition. Integral membrane proteins and non-integral membrane proteins were analyzed separately. The average deviation from this neutral model shows that there is a selective pressure increasing content in charged amino acids for non-integral membrane proteins, and content in hydrophobic amino acids for integral membrane proteins. Amino-acid frequencies were greatly influenced by genomic G+C content, but the influence was found to be often weaker than predicted. This may be evidence for a selective pressure, maintaining most amino-acid frequencies close to an optimal value. Concordance between the genetic code and protein composition is discussed in the light of this observation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / analysis*
  • Bacterial Proteins / chemistry*
  • Cytosine / analysis*
  • Genome, Bacterial*
  • Guanine / analysis*


  • Amino Acids
  • Bacterial Proteins
  • Guanine
  • Cytosine