MBE Advance Access originally published online on May 11, 2006
Molecular Biology and Evolution 2006 23(7):1444-1449; doi:10.1093/molbev/msl010
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Research Article |
Observations of Amino Acid Gain and Loss during Protein Evolution Are Explained by Statistical Bias

* Division of Mathematical Biology, National Institute of Medical Research, Mill Hill, London, United Kingdom; and
Department of Biological Sciences, Biological Computation and Visualisation Center, Louisiana State University
E-mail: richard.goldstein{at}nimr.mrc.ac.uk.
The authors of a recent manuscript in "Nature" claim to have discovered "universal trends" of amino acid gain and loss in protein evolution. Here, we show that this universal trend can be simply explained by a bias that is unavoidable with the 3-taxon trees used in the original analysis. We demonstrate that a rigorously reversible equilibrium model, when analyzed with the same methods as the "Nature" manuscript, yields identical (and in this case, clearly erroneous) conclusions. A main source of the bias is the division of the sequence data into "informative" and "noninformative" sites, which favors the observation of certain transitions.
Key Words: amino acid bias ancestral reconstruction molecular evolution parsimony