Abstract
The tight junction (zonula occludens) forms a linear region of contact between plasma membranes of adjacent epithelial cells near their juxtaluminar borders. This junction is a seal that prevents free diffusion between luminal and adluminal aspectsoof epithelia. At tight junctions in thin sections, the two apposed 75 Å plasma membranes join to form a membrane complex 140 Å in thickness. There is apparent “fusion” of the membranes with loss of outer leaflet material of one or both of the membranes. Previous interpretations of freeze-cleaved (and etched) tight junctions have been based on the Moor-Muhlethaler hypothesis that true membrane surfaces are revealed by cleaving. However, there is now compelling evidence that the surfaces revealed by cleaving are generated by splitting frozen membranes along a central plane thereby creating two new surfaces: Face A oriented toward the extracellular compartment and Face B directed toward the cytoplasm. We now describe a distinctive intramembranous fibrillar component in plasma membranes at tight junctions as revealed by membrane splitting.
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Schedule a callMore From: Proceedings, annual meeting, Electron Microscopy Society of America
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