MBE Advance Access originally published online on July 20, 2006
Molecular Biology and Evolution 2006 23(10):1852-1862; doi:10.1093/molbev/msl064
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Published by Oxford University Press 2006.
Research Article |
Mutation-Biased Adaptation in a Protein NK Model
Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute; and Biochemical Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland
E-mail: arlin.stoltzfus{at}nist.gov.
Evolutionary trends responsible for systematic differences in genome and proteome composition have been attributed to GC:AT mutation bias in the context of neutral evolution or to selection acting on genome composition. A possibility that has been ignored, presumably because it is part of neither the Modern Synthesis nor the Neutral Theory, is that mutation may impose a directional bias on adaptation. This possibility is explored here with simulations of the effect of a GC:AT bias on amino acid composition during adaptive walks on an abstract protein fitness landscape called an "NK" model. The results indicate that adaptation does not preclude mutation-biased evolution. In the complete absence of neutral evolution, a modest GC:AT bias of realistic magnitude can displace the trajectory of adaptation in a mutationally favored direction, to such a degree that amino acid composition is biased substantially and persistently. Thus, mutational explanations for evolved patterns need not presuppose neutral evolution.
Key Words: mutation bias • GC content • NK model • simulation • adaptive evolution • adaptive walk
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