Cell-surface expression of the Rho-tagged ORs cotransfected with the N-terminal Ala replacement mutants of RTP1S. Each combination of mutants of RTP1s and ORs (Olfr599, Olfr1377, and Olfr1484) was transfected into HEK293T cells, and the cell-surface expression level was measured. The results from two independent experiments are shown in each graph. x axis, PE fluorescence; y axis, cell number. The geometric mean of the PE fluorescence of each measurement was used for comparison. The values of RTP1S and OR only were used as positive (= 1) and negative controls (= 0), respectively. Comparison of the normalized response was by different experiments. R2 values were calculated by Pearson's correlation coefficient from the linear regression analysis.