Fig. 3. Distribution of proteins between membrane and cytosol in the postnuclear supernatant. (A) Triton soluble membranes (TX100), triton insoluble membranes (SDS) and cytosol (S100) from E14 rat telencephalon homogenate postnuclear supernatant (PNS) were prepared with either magnesium ions (Mg²⁺ group) or a chelating agent (EDTA group), separated by SDS-PAGE, and visualized by western blot. The presence of either Mg²⁺ or EDTA resulted in no reproducible differences in the molecular distributions between cytosol, Triton soluble membranes and Triton insoluble membranes. (B,C) Integrated density plots of the distribution of MALS, CASK and Mint proteins in an iodixanol density gradient (B), with the corresponding western blots of the different fractions (C). The distributions of MALS and CASK showed a strong similarity. (D,E) Integrated density plots of the distribution of known cell polarity proteins (D), together with corresponding western blots (E), reveal the distribution of several cell polarity proteins found in NPCs. Taken together, the data suggest that MALS might interact with CASK and PALS1 in NPCs based on a similar cellular localization. (F) Bars represent the cellular distribution of proteins known to associate with different subcellular compartments (based on data shown in Fig. S4 in the supplementary material).