Cells co-expressing Ctr4-VN and Ctr4-VC in the presence of Ctr5-Myc₁₂ display a fluorescent signal at the plasma membrane, whereas Ctr5-VN and Ctr5-VC co-expressed in the presence of Ctr4-Flag₂ fail to interact at the plasma membrane.

A, The strain JSY22 (ctr4Δ ctr5Δ) was co-transformed with vectors alone (v. alone), integrative plasmids co-expressing only ctr4+-VN and ctr4+-VC, or ctr4+-VN and ctr4+-VC in the presence of ctr5+-MYC12. Cells were grown either for 5 days on YES medium in the presence of glucose or, for 9 days, on YES medium in the presence of glycerol/ethanol (EtOH) containing or not BCS (25 µM). WT, parental wild-type strain FY435. B, ctr4Δ ctr5Δ cells co-expressing the indicated fusion alleles were grown to an A600 of 0.5. At this optical density, BCS (100 µM) was added and the treated cultures were incubated for 3 h at 30°C, and then visualized for BiFC by fluorescence microscopy. The cells were also examined by Nomarski microscopy for cell morphology. C, JSY22 (ctr4Δ ctr5Δ) cells were co-transformed with vectors alone, or with ctr5+-VN and ctr5+-VC in the absence (v. alone) or the presence of ctr4+-FLAG2. Growth was tested on both fermentable (glucose) and non-fermentable (glycerol/ethanol) media that were either supplemented, or not with BCS (25 µM). D, BiFC analysis of Ctr5-VN + Ctr5-VC and Ctr5-VN + Ctr5-VC + Ctr4-FLAG2 in ctr4Δ ctr5Δ cells. Representative fluorescence images of BiFC are shown. Nomarski microscopy was used to determine cell morphology.