Involvement of Helices at the Dimer Interface in ClC-1 Common Gating

ClC-1 is a dimeric, double-pored chloride channel that is present in skeletal muscle. Mutations of this channel can result in the condition myotonia, a muscle disorder involving increased muscle stiffness. It has been shown that the dominant form of myotonia often results from mutations that affect the so-called slow, or common, gating process of the ClC-1 channel. Mutations causing dominant myotonia are seen to cluster at the interface of the ClC-1 channel monomers. This study has investigated the role of the H, I, P, and Q helices, which lie on this interface, as well as the G helix, which is situated immediately behind the H and I helices, on ClC-1 gating. 11 mutant ClC-1 channels (T268M, C277S, C278S, S289A, T310M, S312A, V321S, T539A, S541A, M559T, and S572V) were produced using site-directed mutagenesis, and gating properties of these channels were investigated using electrophysiological techniques. Six of the seven mutations in G, H, and I, and two of the four mutations in P and Q, caused shifts of the ClC-1 open probability. In the majority of cases this was due to alterations in the common gating process, with only three of the mutants displaying any change in fast gating. Many of the mutant channels also showed alterations in the kinetics of the common gating process, particularly at positive potentials. The changes observed in common gating were caused by changes in the opening rate (e.g. T310M), the closing rate (e.g. C277S), or both rates. These results indicate that mutations in the helices forming the dimer interface are able to alter the ClC-1 common gating process by changing the energy of the open and/or closed channel states, and hence altering transition rates between these states

Muscle cell membranes and chloride ions

Thesis (Ph.D.) -- University of Adelaide, Dept. of Human Physiology and Pharmacology, 197

Structure and function of CLC Chloride Channels

CLC voltage-gated chloride ion channels (and transporters) family is widely present in bacteria to humans from a variety of species, is responsible for regulation of chloride ion transmembrane anion transport. CLC channel proteins Jie Wei diamond homodimer each triangle monomer by 18 α-helix structure, has its own independent pore (pore) and selective filters (selectivity filter), and its internal symmetry was a double reverse parallel structures. CLC channels and transporter proteins ( ClC-0, -1, -2) of the gating mechanisms (gating) and infiltration of the mechanism (permeation) and chloride ion in the pore within the binding capacity (binding) closely related to the family show distinctive electrophysiological properties . its mammalian family members entrusted with regulation of muscle cell membrane excitability and movement in skin cells, transport, regulation of cell volume and the acidification of intracellular organelles such as the mission, so its function will lead to defects in myotonia, Bartter syndrome, Dent disease and bone Petrochemical springing a variety of genetic diseaseMa Linlin, Fu Song-bin and Bretag Alla

Interaction of hydrophobic anions with the rat skeletal muscle chloride channel ClC-1: effects on permeation and gating

The definitive version is available at www.blackwell-synergy.comPermeation of a range of hydrophobic anions through the rat skeletal muscle chloride channel, rClC-1, expressed in Sf-9 (a Spodoptera frugiperda insect cell line) cells has been studied using the whole-cell patch-clamp technique. Bi-ionic reversal potentials measured with external application of foreign anions gave the following permeability sequence: Cl- (1) > benzoate (0.15) > hexanoate (0.12) > butyrate (0.09) > propionate (0.047) approximately formate (0.046). Anions with larger hydrophobic moieties were more permeant, which suggested that ClC-1 selectivity for hydrophobic anions is dominated by their interaction with a hydrophobic region in the external mouth of the pore. All anions studied when applied from outside show an apparently paradoxical voltage-dependent block of inward currents; this voltage-dependent block could be qualitatively described by a discrete-state permeation model with two binding sites and three barriers. Effects of the external anions with aliphatic side-chains on the apparent open probability (Po) suggested that they are unable to gate the channel, but can modulate ClC-1 gating, probably, by changing Cl- affinity to the gating site. Effects of internal application of benzoate, hexanoate or propionate mimicked those of increasing internal pH, and similarly depended on the channel protonation from the external side. Results for internal benzoate support the concept of a negatively charged cytoplasmic particle being involved in the ClC-1 gating mechanism sensitive to the internal pH.Grigori Y. Rychkov, Michael Pusch, Michael L. Roberts, and Allan H. Breta

Characteristics of skeletal muscle chloride channel CIC-1 and point mutant R3045 expressed in Sf-9 insect cells

Astill, D.St.J. ; Rychkov, G. ; Clarke, J.D. ; Hughes, B.P. ; Roberts, M.L. ; Bretag, A.H