Journal
GENETICS
Volume 179, Issue 2, Pages 977-984Publisher
OXFORD UNIV PRESS INC
DOI: 10.1534/genetics.108.089185
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Funding
- NIGMS NIH HHS [GM079536, R01 GM079536] Funding Source: Medline
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Although protein evolution can be approximated as a molecular evolutionary clock, it is well known that sequence change departs from a clock-like Poisson expectation. Through studying the deviations from a molecular clock, insight can be gained into the forces shaping evolution at the level of proteins. Generally, substitution patterns that show greater variance than the Poisson expectation are said to be overdispersed. Overdispersion of sequence change may result from temporal variation in the rate at which amino acid substitutions occur on a phylogeny. By comparing the genomes of four species of yeast, five species of Drosophila, and five species of mammals, we show that the extent of overdispersion shows a strong negative correlation with the effective Population size of these organisms. Yeast proteins show very little overdispersion, while mammalian proteins show substantial overdispersion. Additionally, X-linked genes, which have reduced effective population size, have gene products that show increased overdispersion in both Drosophila and mammals. Our research suggests that mutational robustness is more pervasive in organisms, with large population sizes and that robustness acts to stabilize the molecular evolutionary clock of sequence change.
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