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1. Shaker B K+ channels, expressed in the insect cell line Sf9, were studied in zero K+, Na+ or N-methyl-D-glucamine (NMG)-containing solutions. In the absence of K+ ions on both sides of the membrane, the K+ conductance collapsed with the delivery of short depolarizing pulses that activated the channels. The collapse of the conductance was fully prevented(More)
Recently, patch-clamping of yeast protoplasts has revealed the presence of plasma membrane K+ channels (Gustin, M. C., B. Martinac, Y. Saimi, M. R. Culberston, and C. Kung. 1986. Science (Wash. DC). 233:1195-1197). In this work we show that fusion of purified plasma membranes into planar bilayers allows the study of the yeast channels. The main cationic(More)
The Shaker B K(+) conductance (G(K)) collapses (in a reversible manner) if the membrane is depolarized and then repolarized in, 0 K(+), Na(+)-containing solutions (Gómez-Lagunas, F. 1997. J. Physiol. 499:3-15; Gómez-Lagunas, F. 1999. Biophys. J. 77:2988-2998). In this work, the role of Na(+) ions in the collapse of G(K) in 0-K(+) solutions, and in the(More)
In the absence of K(+) on both sides of the membrane, delivery of standard activating pulses collapses the Shaker B K(+) conductance. Prolonged depolarizations restore the ability to conduct K(+). It has been proposed that the collapse of the conductance results from the dwelling of the channels in a stable closed (noninactivated) state (, J. Physiol.(More)
In this work, we studied the characteristics of recovery from desensitization of the light-elicited current of crayfish. Applying a two-flash protocol, we found that the first flash triggers a current that activates with a noticeable latency, reaches a peak value, and thereafter decays along a single exponential time course. In comparison with the(More)
Protein mobility is important to achieve protein function. Intrinsic flexibility associated with motion underlies this important issue and the analysis of side chain flexibility gives insights to understand it. In this work, the S5-P-S6 pore modulus (PM) of members of Kv and HCN channels was examined by a combination of sequence alignment, residue(More)
Visual photoreceptors are structures involved in the expression and synchronization of crayfish circadian rhythm of sensitivity to light (electroretinogram, ERG). Considering the relevant role of Pigment dispersing hormone (PDH) in the invertebrate circadian system organization, we study the effect of this substance on the electrical activity of crayfish(More)
In this communication we reported the study of a cation channel present in the cytoplasmic membrane of the nitrogen fixing bacterium Rhizobium etli. Inner-membrane (IM) vesicles were purified and fused into planar lipid bilayers (PLBs), under voltage clamp conditions. We have found that fusion of IM-enriched vesicle fractions with these model membranes(More)
Shab channels are fairly stable with K(+) present on only one side of the membrane. However, on exposure to 0 K(+) solutions on both sides of the membrane, the Shab K(+) conductance (G(K)) irreversibly drops while the channels are maintained undisturbed at the holding potential. Herein it is reported that the drop of G(K) follows first-order kinetics, with(More)
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