TABLE 2

Relative affinities between two BRET partners of melatonin receptors

The BRET50 represents the acceptor/donor ratio required to reach half-maximal BRET in BRET-donor saturation experiments. Results are the mean + S.E. of 7 to 10 independent saturation curves (Fig. 2). Receptor densities at BRET50 are determined by averaging BRET values recorded close to the calculated BRET50 of 7 to 10 individual saturation experiments. The luciferase activity and YFP fluorescence were used to calculate the number of 125I-MLT binding sites according to standard curves shown in Fig. 1 of supplemental material; 7500 HEK 293 cells correspond to 1 μg of total protein.

Condition Dimers Receptor Density at BRET50
BRET50 Receptor/Cell fmol/mg of protein
1 MT1-Rluc/MT1-YFP 3.7 ± 0.8 3080 ± 520 33 ± 4
2 MT1-Rluc/MT2-YFP 3.0 ± 1.6 3434 ± 436 43 ± 5
3 MT2-Rluc/MT1-YFP 4.2 ± 1.6 4554 ± 974 51 ± 12
4 MT2-Rluc/MT2-YFP 12.5 ± 2.2** 11318 ± 2176** 142 ± 27**
  • ** , P < 0.02, compared with conditions 1, 2, and 3.