High-level expression, functional reconstitution, and quaternary structure of a prokaryotic ClC-type chloride channel.

ClC-type anion-selective channels are widespread throughout eukaryotic organisms. BLAST homology searches reveal that many microbial genomes also contain members of the ClC family. An Escherichia coli-derived ClC Cl(-) channel homologue, "EriC," the product of the yadQ gene, was overexpressed in E.

Homodimeric architecture of a ClC-type chloride ion channel.

The recent discovery of the ClC-family of anion-conducting channel proteins has led to an appreciation of the central roles played by chloride ion channels in cellular functions, such as electrical behaviour of muscle and nerve and epithelial solute transport. Little is known, however, about molecular architecture or sequence-function relationships in these membrane proteins. In the single case of ClC-0, a voltage-gated 'muscle-type' chloride channel, the functional complex is known to be a homo-oligomer of a polypeptide of Mr approximately 90,000, with no associated 'helper' subunits.

Purification, reconstitution, and subunit composition of a voltage-gated chloride channel from Torpedo electroplax.

The voltage-gated Cl- channel from Torpedo electroplax was purified in functional form by an immunoaffinity procedure. Channel activity was assayed by 36Cl- uptake into reconstituted liposomes and by direct recording after insertion into planar lipid bilayers. The purified channel displays the same "double-barreled" gating kinetics observed with native membranes, as well as the correct single-channel permeation characteristics.

The charybdotoxin receptor of a Shaker K+ channel: peptide and channel residues mediating molecular recognition.

Charybdotoxin (CTX) is a peptide of known structure that inhibits Shaker K+ channels by a pore-blocking mechanism. Point mutagenesis of all 30 solvent-exposed residues identified the part of the CTX molecular surface making contact with the receptor in the K+ channel. All close-contact residues are clustered in a well-defined interaction surface; the shape of this surface implies that the outer opening of the Shaker channel conduction pore abruptly widens to a 25 x 35 A plateau.

Light/dark labeling differences in chloroplast membrane polypeptides associated with chloroplast coupling factor o.

The fluorogenic reagent fluorescamine has been used to determine the labeling patterns of Type C spinach chloroplast membrane polypeptides. Membrane polypeptides labeled with fluorescamine were detected by scanning high resolution sodium dodecyl sulfate polyacrylamide gradient slab gels for fluorescence emission. Three membrane polypeptides show a decrease in the extent of labeling when chloroplast membranes are labeled in the light compared to when they are labeled in the dark.