| Quantitative understanding of how the strength of a protein-protein interaction is related to its biological function is a prerequisite for modeling biological systems. The interaction between Sho1 and Pbs2 is required for signaling through the HOG pathway via Ste11 in yeast. This system has been used to quantitatively assess how the binding affinity of two interacting proteins affects signal transduction. Here, it was shown that the binding affinity of Sho1 for Pbs2 is linearly correlated with the ability of mutant Sho1 SH3 domains to activate the HOG pathway. Furthermore, decreased binding affinity was also correlated with an increase in cross talk to the pheromone response pathway upon hyperosmotic stress. It was also found that Sho1 utilizes a second binding surface on its SH3 domain to activate the cross talk response. |
