Tight junctions: architecture of plasma membranes at sites of cell-cell "fusion" in relation to paracellular permeability.

A major goal in analyzing the structure of tight junctions by freeze-fracture has been to create a generalized model for this membrane specialization conforming to both physiological and morphological data, and providing a basis for understanding variation in tight junction appearance and function. In the present review we have focused on some of the problems involved. Results obtained by double replication, rotary shadowing and rapid freezing are discussed. A model for tight junctions with a general scaffolding of inverted lipid micelles (cylinders) binding the adjacent membranes together, and associated with integral membrane proteins of significance, for instance, in stabilization as well as in regulation of permeability, appears promising.