title: Quantitative effect of scaffold abundance on signal propagation.
abstract: Protein scaffolds bring together multiple components of a signalling pathway, thereby promoting signal propagation along a common physical 'backbone'. Scaffolds play a prominent role in natural signalling pathways and provide a promising platform for synthetic circuits. To better understand how scaffolding quantitatively affects signal transmission, we conducted an in vivo sensitivity analysis of the yeast mating pathway to a broad range of perturbations in the abundance of the scaffold Ste5. Our measurements show that signal throughput exhibits a biphasic dependence on scaffold concentration and that altering the amount of scaffold binding partners reshapes this biphasic dependence. Unexpectedly, the wild-type level of Ste5 is approximately 10-fold below the optimum needed to maximize signal throughput. This sub-optimal configuration may be a tradeoff as increasing Ste5 expression promotes baseline activation of the mating pathway. Furthermore, operating at a sub-optimal level of Ste5 may provide regulatory flexibility as tuning Ste5 expression up or down directly modulates the downstream phenotypic response. Our quantitative analysis reveals performance tradeoffs in scaffold-based modules and defines engineering challenges for implementing molecular scaffolds in synthetic pathways.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Chapman
authors.forename: Anand R
authors.initials: AR
authors.lastname: Asthagiri
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010641:Phenotype; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C080321:STE5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C119844:STE7 protein, S cerevisiae