Table 2.

Functional characterization of selected MC4R orthologs or mutants.

Ortholog or mutant	Number of independent experiments	α-MSH-stimulated cAMP, EC50 (nM)	Eu-labeled NDP-α-MSH displacement binding, IC50 (nM)
Human WT	3	4.205 ± 0.9714	NDa
Human Q156R	3	1.283 ± 0.1242b	NDa
Blue whale WT	3	1.445 ± 0.0328	18.24 ± 3.565
Blue whale Q156R	3	1.058 ± 0.1318b	9.379 ± 1.515b

For functional characterization, HEK293T cells were transiently transfected with MC4R or their mutant constructs. cAMP assays were performed using α-MSH, and unlabeled NDP-α-MSH was used to displace Eu-labeled NDP-α-MSH in binding assays. EC₅₀ values were determined from concentration-response curves of agonists (1pm to 1 μm) using GraphPad Prism; IC₅₀ values were determined from concentration-response curves of agonists (0.1pm to 1 μm) using GraphPad Prism. The data were expressed as the mean ± SEM of three independent experiments for the MC4R orthologs or mutants. ^aND, not done. ^bSignificantly different from corresponding WT receptor, p < 0.05.