Journal of Molecular Evolution

, Volume 57, Issue 6, pp 731–736 | Cite as

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



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 



Helpful comments were provided by C.P. Kurtzman, D.P. Labeda, T.J. Ward, J. Zhang, and two anonymous reviewers.


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Copyright information

© Springer-Verlag New York Inc. 2003

Authors and Affiliations

  1. 1.Microbial Genomics and Bioprocessing Research UnitNational Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria, IL 61604USA

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