Journal of Molecular Evolution

, Volume 57, Issue 6, pp 731-736

First online:

Selection for Highly Biased Amino Acid Frequency in the TolA Cell Envelope Protein of Proteobacteria

  • Alejandro P. RooneyAffiliated withMicrobial Genomics and Bioprocessing Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria, IL 61604 Email author 

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The bacterial cell envelope protein TolA functions to maintain the integrity of the cell membrane. This protein contains high levels of alanine and lysine that are used in the formation of alpha helices, which are required for normal protein function. The neutral model of molecular evolution predicts that amino acid composition and nucleotide composition are driven by the underlying GC content, as a result of mutation bias. However, this study shows that selection has acted to maintain high levels of alanine and lysine in the TolA protein of Proteobacteria, which in turn has biased nucleotide composition in the corresponding tolA gene.


TolA Cell membrane Selection Amino acid composition