title: Protein-protein interaction affinity plays a crucial role in controlling the Sho1p-mediated signal transduction pathway in yeast.
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.
authors.affiliation: Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Marles
authors.forename: Samira
authors.initials: S
authors.lastname: Dahesh
authors.forename: Jennifer
authors.initials: J
authors.lastname: Haynes
authors.forename: Brenda J
authors.initials: BJ
authors.lastname: Andrews
authors.forename: Alan R
authors.initials: AR
authors.lastname: Davidson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D008565:Membrane Proteins; C459787:SHO1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C088589:HOG1 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases