Figure 3

Claudins are membranous proteins harbouring two extracellular loops (EL-1 and EL-2) and one small intracellular loop. The larger EL-1 loop regulates solute permeability and charge selectivity while the smaller EL-2 loop establishes contacts with the neigbouring cell. There are four transmembrane domains in claudin molecules. By the carboxyterminal part the claudin molecule attaches to the scaffolding proteins of the tight junctions.