| description | Protein which is part of an anion channel found in the plasma membrane and in intracellular membranes. These channels are permeable for various anions, such as iodide, bromide, but also for nitrates, phosphates and even negatively charged amino acids. They are called chloride channels, because chloride is the most abundant anion and the predominant permeating species in all organisms. They have been classified according to their gating mechanisms, which may depend on changes in the transmembrane electric field (voltage-dependent/gated chloride channels, e.g. ClC family), on a protein kinase/nucleotide mediated mechanism (CFTR), an increase in intracellular calcium (calcium activated chloride channels, e.g. CaCC), cell swelling (volume-regulated anion channels, e.g. VRAC) or binding of a ligand, e.g. glycine or - aminobutyric acid (GABA) activated channels. In contrast with cation channels, they are not involved in the initiation or spread of excitation, but in the regulation of excitability in nerve and muscle. They also participate in many housekeeping processes, such as volume regulation, pH regulation in organelles, electrogenesis and control of synaptic activity. The chloride channels are crucial for transepithelial transport and the control of water flow, and often provide unexpected permeation pathways for a large variety of anions |
