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• Articles by M.L. Kelly
• Articles by D.J. Woodbury

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• Curare binding and the curare-induced subconductance state o...

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• Two Domains in Dihydropyridine Receptor Activate the Skeleta...

  Two Domains in Dihydropyridine Receptor Activate the Skeletal Muscle Ca Release Channel Biophysical Journal, Volume 81, Issue 3, 1 September 2001, Pages 1419-1429 Mirko Stange, Ashutosh Tripathy and Gerhard Meissner Abstract The II-III cytoplasmic loop of the skeletal muscle dihydropyridine receptor (DHPR) -subunit is essential for skeletal-type excitation-contraction coupling. Single channel and [H]ryanodine binding studies with a full-length recombinant peptide (p) confirmed that this region specifically activates skeletal muscle Ca release channels (CRCs). However, attempts to identify shorter domains of the II-III loop specific for skeletal CRC activation have yielded contradictory results. We assessed the specificity of the interaction of five truncated II-III loop peptides by comparing their effects on skeletal and cardiac CRCs in lipid bilayer experiments; p and p specifically activated the submaximally Ca-activated skeletal CRC in experiments using both mono and divalent ions as current carriers. A third peptide, p, showed a bimodal activation/inactivation behavior indicating a high-affinity activating and low-affinity inactivating binding site. Two other peptides (p and p) that contained an RKRRK-motif and have previously been suggested in in vitro studies to be important for skeletal-type E-C coupling, failed to specifically stimulate skeletal CRCs. Noteworthy, p, p, and p induced similar subconductances and long-lasting channel closings in skeletal and cardiac CRCs, indicating that these peptides interact in an isoform-independent manner with the CRCs. Abstract | Full Text | PDF (284 kb)

• Single-channel currents from acetylcholine receptors in embr...

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Abstract

Cholinergic synaptic vesicles were isolated from the electric organ of Torpedo californica. Vesicle membrane proteins were reconstituted into planar lipid bilayers by the nystatin/ergosterol fusion technique. After fusion, a variety of ion channels were observed. Here we identify four channels and describe two of them in detail. The two channels share a conductance of 13 pS. The first is anion selective and strongly voltage dependent, with a 50% open probability at membrane potentials of -15 mV. The second channel is slightly cation selective and voltage independent. It has a high open probability and a subconductance state. A third channel has a conductance of 4–7 pS, similar to the subconductance state of the second channel. This channel is fairly nonselective and has gating kinetics different from those of the cation channel. Finally, an approximately 10-pS, slightly cation selective channel was also observed. The data indicate that there are one or two copies of each of the above channels in every synaptic vesicle, for a total of six channels per vesicle. These observations confirm the existence of ion channels in synaptic vesicle membranes. It is hypothesized that these channels are involved in vesicle recycling and filling.