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

• Published in: Gene Vol. 205; no. 1; pp. 309 - 316
• Main Author: Lobry, J.R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 31.12.1997; Elsevier
• Subjects: Amino Acids - analysis; Bacterial Proteins - chemistry; Correspondence analysis; Cytosine - analysis; Directional mutation pressure; Genetic code; Genome, Bacterial; Guanine - analysis; Integral membrane proteins; Life Sciences; Other; Integral membrane proteins; Directional mutation pressure; Genetic code; Correspondence analysis
• ISSN: 0378-1119; 1879-0038
• 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.