Figure 1. Purification of total SR proteins. Aliquots were taken at different steps of the purification and analyzed by SDS‐PAGE followed by Coomassie staining (a) and Western blotting (b), using an anti‐SR protein monoclonal antibody (10H3). The lanes are identified as follows: 1, initial HeLa nuclear extract (1/8000 of the total volume); 2, pellet of the 55% (NH ₄) ₂SO ₄ precipitation (1/2000); 3, pellet of the 90% (NH ₄) ₂SO ₄ precipitation (1/1000); 4, supernatant of the MgCl ₂ precipitation (1/1000); 5, purified total SR proteins (1/300). In the doublet of SRp30 species, which contains SRSF1, SRSF2, SRSF7 and SRSF9, SRSF7 is concentrated in the upper band while SRSF1 is in the lower band.

Figure 2. Purification of 6 × His‐tagged SRSF1 from baculovirus‐infected Sf9 cells. Aliquots were taken at different steps during the purification and analyzed by SDS‐PAGE and Coomassie staining. Lanes 1 and 2 correspond respectively to the lysate before and after centrifugation (1/20 000 of the total volume was analyzed). Lanes 3 to 10 correspond to different steps of the TALON® chromatography: 1/20 000 of flow‐through (lane 3), 1/600 of the 15 mM imidazole wash (lane 4), and of fractions eluted with 50 mM (lanes 5 and 6), 200 mM (lanes 7 and 8) and 500 mM (lanes 9 and 10) imidazole.