GukH binding site on the Dlg GK. (a) Schematic representation of yeast two-hybrid bait and prey constructs. AD = activation domain, DBD = DNA binding domain. (b) Representative results from yeast two-hybrid assay. Serial dilution onto plates of permissive (-LT) or selective (-L-T-H + 3AT) medium starting with A600 of 0.5 shows loss of interaction between GukH and the Dlg GK domain with tyrosine 855 mutated to alanine. (c) Summary of yeast two-hybrid results. Yeast growth indicates interaction (+) while no growth indicates no interaction (-).Mutations that repress GukH binding but not SH3 binding are mapped onto the PSD-95 GK structure (22; PDB code: 1kjw). The Lid, Core, and GBD domains are colored in blue, green, and red, respectively. The location of the SH3 domain is shown.