Fig. 4: Lipids influence the GLUT5 activity in proteoliposomes.

a Time-dependent uptake of ¹⁴C-d-fructose by rGLUT5 reconstituted into liposomes prepared using brain-fraction-seven lipids (filled circles) and liposomes prepared using a synthetic brain-fraction-seven lipid mixture (empty circles). Non-specific uptake was recorded using protein-free liposomes of brain-fraction-seven (filled squares) and the synthetic-brain-seven lipid mixture (empty squares), respectively. Error bars indicate mean ± s.e.m. of n = 3 independent experiments. b Relative rGLUT5 [¹⁴C]-d-fructose uptake after 2 min using proteoliposomes prepared from synthetic-brain-seven lipids. Individual lipids were omitted as follows: POPS, POPC, SM, POPI, Cerebroside, and POPE. Black bars represent specific rGLUT5 transport after subtraction of unspecific transport and normalized to the intensity of synthetic-brain-seven lipid mixture (synthetic BF7) where no lipids were removed. Error bars indicate mean ± s.e.m. of n = 9 independent experiments for synthetic BF7, -POPS, -POPC, -POPI, -Cerebroside and mean ± s.e.m. of n = 9 independent experiments for -SM. c Effect on rGLUT5 transport by titration of POPC/POPS in synthetic-brain-seven lipid mixture proteoliposomes.¹⁴C-d Fructose uptake was recorded after 2 min. Pie charts on top of each black bar represent the modified lipid concentrations; in black POPC, in blue POPS, and the remaining composition in clear gray. Data was represented as in (b), and Error bars indicate mean ± s.e.m. of n = 6 independent experiments. d Effect on rGLUT5 transport by titration of POC/POPE in synthetic-brain-seven proteoliposomes. As in c, POPE is represented in cyan. Data were represented as in (b); error bars indicate mean ± s.e.m. of n = 6 independent experiments. e Relative rGLUT5 ¹⁴C-d-fructose transport after 2 min in synthetic brain-fraction-seven proteoliposomes. POPC (18:1) was substituted for the greater unsaturated lipid PC (18:6) and DOPC (18:2). Error bars indicate mean ± s.e.m. of n = 9 independent experiments for PC (18:1) and PC (18:6) and mean ± s.e.m. of n = 7 independent experiments for PC (18:2). f Effect on rGLUT5 transport by titration of POPC/DOPC in synthetic brain-fraction-seven proteoliposomes. As in c and d, but DOPC is represented in dark orange; error bars indicate mean ± s.e.m. of n = 6 independent experiments.