Fig. 2

NR7 ligand-binding domain (LBD) does not heterodimerize with RXR. A, B Native mass spectrometry analysis of A the NR7 LBD alone and B the mixture NR7 LBD-RXR LBD. The different charge states of the isolated NR7 and RXR LBDs are given in grey and orange, respectively, above the m/z peaks. An α-N-6-gluconoylation modification (+178 Da, labeled with a star) of the N-terminal His₆-tag used for protein purification is seen in a fraction of the protein, for both NR7 and RXR LBDs (grey and orange stars respectively). C Native mass spectrometry analysis of the human PPARα and amphioxus RXR LBDs. The different charge states of the isolated PPARα and RXR LBDs are given in blue and orange, respectively, above the m/z peaks. An α-N-6-gluconoylation modification (+178 Da, labeled with a star) of the N-terminal His₆-tag used for protein purification is seen in a fraction of the protein, for both LBDs (given in colored stars). Peaks corresponding to the PPARα /RXR LBD complex are clearly detected (blue labels), corresponding to PPARα/RXR heterodimer formation. D Native polyacrylamide gel electrophoresis of amphioxus NR7 with amphioxus RXR and human PPARα and amphioxus RXR with different molar ratios indicated on the right side of the figure. Upper and middle panels: different molar ratios of RXR:NR7 were considered, by varying the quantity of RXR (upper) or NR7 (middle). No band is seen that could correspond to a heterodimer. Lower panel: different RXR:PPARα molar ratios were tested. For some RXR:PPARα ratios, an additional band (marked by a star) is observed, which corresponds to a RXR-PPARα heterodimer