Chloride channel
As chloride channels transporters are referred to in the physiology and cell biology, which have a specific and more or less selective conductance for chloride ions. The subfamily of the epithelial calcium- regulated chloride channels ( ClC - E ) can be seen as a separate group because their channel function has become questionable and they do not have the CBS domain of the ClC family.
The protein family of chloride channels ( ClC, derived from the English chloride channel ) comprises chloride channels and secondary active chloride / proton exchanger. Structural homologues of this family are found across all biological kingdoms through, from simple intestinal bacterium Escherichia coli and plants to mammals. Here, the channels perform different biological functions, such as participation in the regulation of the cellular water balance or the stabilization of the resting membrane potential in skeletal muscle.
Scientific History
Discovered in 1980 to Miller et al. the first chloride channel in vesicles of the electric organ of Torpedorochens. On the basis of single-channel studies, he predicted a doppelporigen channel, which has since been solidified by a variety of studies. In the 1990s, Thomas Jentsch examined the protein family at the molecular level. 2002 sparked R. Dutzler X-ray crystallography ( 2.5-3.5 Å), the structures of ClC transporter EcClC and StClC of E. coli and Salmonella typhi and hereby set the basis for the molecular understanding of the function.
Isoforms in human
In humans, there are nine isoforms of the ClC family. Some of them are expressed in the plasma membranes of other intracellular in the membranes of organelles. ClC -1, for example, found in the plasma membrane of skeletal muscle cells and is involved in the stabilization of the resting membrane potential.
The individual human chloride transporter: ClC -1, ClC -2, ClC -3, ClC -4, ClC -5, ClC -6, ClC -7, ClC -8, ClC- ninth
Chloride channels in plants
Chloride channels have different functions in plants, depending on their localization and their ion affinity. The best studied are the seven chloride channels from Arabidopsis thaliana, AtCLCa to AtCLCg. The channels are located in the membranes of various organelles and there fulfill the function of Aniontransportern. To carry AtCLCa and AtCLCe nitrate in place of chloride across membranes.
The structure
ClC transporters and channels are diamond-shaped homodimers. Each subunit has its own hourglass shaped pore with the narrowest point at the center of the membrane. From the extra-and intracellular side rich two broad water-filled atria into the pore, the pore centrally located anhydrous ago. Will be accepted three ion binding sites: two at the contact surface between the atrium and pore interior and in the anhydrous center. Are coordinated ions in the permeation case of partially charged side chain hydroxyl groups and some main chain nitrogen atoms, which together form the selectivity filter and the ion energy balance by the hydrophobic part of the membrane.