Fig. 5.

The ²³FQNLF²⁷ motif promotes NTD–LBD interactions within a single molecule. (A) Deletion of the ²³FQNLF²⁷ motif had no effect on the DHT dose–response (EC₅₀ ≈ 1–3 nM) of CFP–AR–YFP FRET in HEK293 cells (detected by FPR). The overall level of CFP–ARΔ–YFP was lower than CFP–AR–YFP FRET. (B) Comparison of CFP–AR/AR–YFP and CFP–ARΔF/ARΔF–YFP association in HeLa cells. AR and ARΔF achieved maximum nuclear FRET at similar acceptor/donor ratios, indicating an equivalent dimerization affinity. Maximal FRET levels were reduced for the ΔF mutants, indicating an altered dimer structure. (C and D) HeLa cells transfected with CFP–AR–YFP (n = 579 total cells at all time points) or CFP–ARΔF–YFP (n = 347 total cells) were imaged by fluorescence microscopy within the nucleus (C) or cytoplasm (D) at various time points after addition of 100 nM DHT. Error bars represent the SEM.