The functional unit of the CLC channels is a dimer with each subunit forming a proper pore. Although the crystal structure of bacterial CLC channels was resolved, the topology of the CLC channels is complex and has not been fully elucidated. It is generally accepted that both the N- and C- terminus domains are intracellular while the number and configuration of the transmembrane domains vary greatly between different models.nCLC-2 is widely distributed with prominent expression in brain, kidney, lung and the gastrointestinal system. Mutations in the CLC-2 channel gene detected in humans are associated with idiopathic generalized epilepsies while disruption of the ClC-2 gene in mice is associated with testicular and retinal degeneration.