FIG. 4.

Rapamycin and analogs promote FKBP12-TOR interactions. The wild-type GAL4(BD)-TOR1 FRB (A and B) and the mutant GAL4(BD)–TOR1-1 FRB (Ser1862Leu) domains (C and D) were coexpressed with the GAL4(AD)-FKBP12 fusion protein in the two-hybrid host SMY4 (fpr1::hisG TOR1-3). (A and C) Cells were resuspended in top agar on the surface of medium lacking histidine and disks bearing rapamycin, the analogs 2, 28, 19, or 23, or no drug were placed on the surface. Growth indicates GAL4-dependent expression of the GAL-HIS3 reporter gene and results from the formation of FKBP12-drug-Tor complexes. (B and D) β-Galactosidase activity was measured by the CPRG assay and was determined in duplicate.