Fig. 4

FRET efficiency for hetero-oligomerization among E protein, regulins (a), and SERCA (b). Ctrl: eGFP-SERCA/mCherry-SERCA pair. PLN^#: FRET values for eGFP-PLN tagged at the luminal end and mCherry-SERCA as a positive control for transmembrane measurements). Pooled data from 3 to 3 independent experiments (for SERCA/E pair: 5 independent experiments) are shown. Dots represent individual cells. Median and interquartile ranges are indicated with box plots. Data were analyzed by Kolmogorov–Smirnov test (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, ns: not significant). (c) The immunoprecipitation experiment using the anti-SERCA IID8 antibody successfully confirmed an association between the eGFP-E protein and mCherry-SERCA2b. Western blot analysis was employed for both the lysates (INPUT) and the eluted fractions (IP), using anti-SERCA IID8 antibody and anti-GFP antibodies as indicated. Non-immune mouse IgG1 was used for IP as a negative control (lanes 3 and 4). Input is ~ 1% of the sample loaded for the immunoprecipitation (~ 1 µg).