Protein-protein interaction affinity plays a crucial role in controlling the Sho1p-mediated signal transduction pathway in yeast |
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Authors: | Marles Jennifer A Dahesh Samira Haynes Jennifer Andrews Brenda J Davidson Alan R |
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Affiliation: | Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada. |
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Abstract: | Protein-protein interactions are required for most cellular functions, yet little is known about the relationship between protein-protein interaction affinity and biological activity. To investigate this issue, we engineered a series of mutants that incrementally reduced the affinity of the yeast Sho1p SH3 domain for its in vivo target, the MAP kinase kinase Pbs2p. We demonstrate a strong linear correlation between the binding energy of these mutants and quantitative in vivo outputs from the HOG high-osmolarity response pathway controlled by Sho1p. In addition, we find that reduction in binding affinity for the correct target within this pathway causes a proportional increase in misactivation of the related mating pheromone response pathway and that strong binding affinity alone does not guarantee efficient biological activity. Our experiments also indicate that a second binding surface on the Sho1p SH3 domain is required for its proper in vivo function. |
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