Fig. 1

Schematic diagram of claudin structure. Left panel. Apposed epithelial cell membranes with one integral-membrane claudin molecule in each cell. Each claudin has four transmembrane segments including two extracellular loops and both the C-terminal and N-terminal ends within the cytoplasm. The extracellular loops of the apposed claudins associate with the respective loops of the adjacent claudin. The right panel depicts each claudin molecule as a sphere within the adjacent cell membranes, represented at a lower magnification than in the left panel. Ion selectivity is imparted to the tight junction by claudin amino acids with a net charge in the first extracellular loop