Fig. 5. Subcellular fractionation of IFN-stimulated BMM. Membrane enriched fractions from post-nuclear supernatants of IFN-stimulated BMM were prepared by separation on a sucrose-step gradient. Fraction I is the 8.5% and fraction II the 20% sucrose layer. The 20-30% and the 30-38% sucrose layer interphases constitute fraction III and IV, respectively. The pellet was designated as fraction V. Golgi and ER membrane-enriched fractions were identified upon SDS-PAGE and western blotting with mAbs against Golgi-associated FTCD and the ER resident protein calnexin. The differential distributions of IIGP, IGTP, mHk3, and -tubulin were analyzed with specific antibodies as described in Materials and Methods.