The charge distribution in the rough endoplasmic reticulum/Golgi complex transitional area investigated by microinjection of charged tracers.
The distribution of microinjected ferritin, ranging in charge from anionic to highly cationic, has been used to indicate differences in surface charge on the rough endoplasmic reticulum and the Golgi complex of intact cells. Highly cationic ferritins (HCF)(HCF1, pI 7.9-9.1; HCF2, pI 8.5-9.4; and HCF3.pI 9.5-10.1) were mostly bound and caused swelling of the rough endoplasmic reticulum. Cationic ferritin (CF) (pI 7.0-8.0) and anionic ferritin (AF) (pI 4.0-4.4) caused no changes in morphology. The distribution of these ferritins in the cytoplasmic space varied with their charge. Significantly more CF was bound to surfaces than was found in the free cytoplasmic space. Conversely, there was significantly more AF in the free cytoplasmic space than close to surfaces. Therefore, the intracellular surfaces are negatively charged. Comparison of the structures in the secretory pathway showed no differences in ferritin binding to transition vesicles, rough endoplasmic reticulum, Golgi saccules or secretory vesicles. The Golgi complex beads are not distinguished by their charge. It is therefore unlikely that charge differences play a role in regulating membrane-membrane interactions in this region of the secretory pathway.
D000818:Animals; D000838:Anions; D002412:Cations; D002683:Chironomidae / Q000648:ultrastructure*; D003593:Cytoplasm / Q000378:metabolism; D004175:Diptera / Q000648:ultrastructure*; D004563:Electrochemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005293:Ferritins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D007526:Isoelectric Point; D008854:Microscopy, Electron; D012469:Salivary Glands / Q000648:ultrastructure
D000838:Anions; D002412:Cations; D005293:Ferritins