Journal
CELL
Volume 150, Issue 1, Pages 222-232Publisher
CELL PRESS
DOI: 10.1016/j.cell.2012.05.033
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Funding
- NSF [0821391]
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [0844442] Funding Source: National Science Foundation
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Orthologous proteins often harbor numerous substitutions, but whether these differences result from neutral or adaptive processes is usually unclear. To tackle this challenge, we examined the divergent evolution of a model bacterial signaling pathway comprising the kinase PhoR and its cognate substrate PhoB. We show that the specificity-determining residues of these proteins are typically under purifying selection but have, in alpha-proteobacteria, undergone a burst of diversification followed by extended stasis. By reversing mutations that accumulated in an alpha-proteobacterial PhoR, we demonstrate that these substitutions were adaptive, enabling PhoR to avoid crosstalk with a paralogous pathway that arose specifically in alpha-proteobacteria. Our findings demonstrate that duplication and the subsequent need to avoid crosstalk strongly influence signaling protein evolution. These results provide a concrete example of how system-wide insulation can be achieved postduplication through a surprisingly limited number of mutations. Our work may help explain the apparent ease with which paralogous protein families expanded in all organisms.
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