Imaging Multiple Conductance States in an Alamethicin Pore

2011 ◽  
Vol 133 (37) ◽  
pp. 14507-14509 ◽  
Author(s):  
Lydia M. Harriss ◽  
Bríd Cronin ◽  
James R. Thompson ◽  
Mark I. Wallace
Keyword(s):  
Conductance States ◽  
Multiple Conductance States

scholarly journals Gap19, a Cx43 Hemichannel Inhibitor, Acts as a Gating Modifier That Decreases Main State Opening While Increasing Substate Gating

2020 ◽  
Vol 21 (19) ◽  
pp. 7340
Author(s):  
Alessio Lissoni ◽  
Nan Wang ◽  
Timur Nezlobinskii ◽  
Maarten De Smet ◽  
Alexander V. Panfilov ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Open Probability ◽  
Transition Analysis ◽  
Transmembrane Pores ◽  
Gating Modifier ◽  
Conductance States ◽  
Multiple Conductance States ◽  
The Impact

Cx43 hemichannels (HCs) are electrically and chemically gated transmembrane pores with low open probability and multiple conductance states, which makes kinetic studies of channel gating in large datasets challenging. Here, we developed open access software, named HemiGUI, to analyze HC gating transitions and investigated voltage-induced HC opening based on up to ≈4000 events recorded in HeLa-Cx43-overexpressing cells. We performed a detailed characterization of Cx43 HC gating profiles and specifically focused on the role of the C-terminal tail (CT) domain by recording the impact of adding an EGFP tag to the Cx43 CT end (Cx43-EGFP) or by supplying the Cx43 HC-inhibiting peptide Gap19 that interferes with CT interaction with the cytoplasmic loop (CL). We found that Gap19 not only decreased HC opening activity to the open state (≈217 pS) but also increased the propensity of subconductance (≈80 pS) transitions that additionally became slower as compared to the control. The work demonstrates that large sample transition analysis allows detailed investigations on Cx43 HC gating and shows that Gap19 acts as a HC gating modifier by interacting with the CT that forms a crucial gating element.

scholarly journals Beticolins, Nonpeptidic, Polycyclic Molecules Produced by the Phytopathogenic Fungus Cercospora beticola, as a New Family of Ion Channel-Forming Toxins

2000 ◽  
Vol 13 (2) ◽  
pp. 203-209 ◽  
Author(s):  
Cyril Goudet ◽  
Marie-Louise Milat ◽  
Hervé Sentenac ◽  
Jean-Baptiste Thibaud
Keyword(s):  
Lipid Bilayers ◽  
Pore Formation ◽  
Phytopathogenic Fungus ◽  
Cercospora Beticola ◽  
Leaf Spot Disease ◽  
Channel Formation ◽  
Channel Conductance ◽  
New Family ◽  
Conductance States ◽  
Multiple Conductance States

Beticolins are toxins produced by Cercospora beticola, a phytopathogenic fungus responsible for the leaf spot disease of sugar beet. They form a family of 20 nonpeptidic compounds (named B0 to B19) that share the same polycyclic skeleton but differ by isomeric configuration (ortho- or para-) and by a variable residue R (bridging two carbons in one of the six cycles). It has been previously shown that B0 assembles itself into a multimeric structure and forms ion channels into planar lipid bilayers (C. Goudet, A.-A. Véry, M.-L. Milat, M. Ildefonse, J.-B. Thibaud, H.Sentenac, and J.-P. Blein, Plant J. 14:359-364, 1998). In the present work, we investigate pore formation by three ortho-beticolins, B0, B2, and B4, and their related (i.e., same R) para-isomers, B13, B1, and B3, respectively, using planarlipid bilayers. All beticolins were able to form ionchannels with multiple conductance states, although the type of cyclization (ortho- or para-) and residue (R) result in variations of channel conductance and ionic permeability, respectively. Channel formation by beticolins is likely to be involved in the biological activity of these toxins.

Electrodiffusional ATP movement through the cystic fibrosis transmembrane conductance regulator

1998 ◽  
Vol 274 (3) ◽  
pp. C799-C809 ◽  
Author(s):  
Horacio F. Cantiello ◽  
George R. Jackson ◽  
Claudio F. Grosman ◽  
Adriana G. Prat ◽  
Steven C. Borkan ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
P Glycoprotein ◽  
Conductance States ◽  
Reported Data ◽  
Multiple Conductance States ◽  
Cystic Fibrosis Transmembrane ◽  
Relevant Component

Expression of the cystic fibrosis transmembrane conductance regulator (CFTR), and of at least one other member of the ATP-binding cassette family of transport proteins, P-glycoprotein, is associated with the electrodiffusional movement of the nucleotide ATP. Evidence directly implicating CFTR expression with ATP channel activity, however, is still missing. Here it is reported that reconstitution into a lipid bilayer of highly purified CFTR of human epithelial origin enables the permeation of both Cl− and ATP. Similar to previously reported data for in vivo ATP currents of CFTR-expressing cells, the reconstituted channels displayed competition between Cl− and ATP and had multiple conductance states in the presence of Cl− and ATP. Purified CFTR-mediated ATP currents were activated by protein kinase A and ATP (1 mM) from the “intracellular” side of the molecule and were inhibited by diphenylamine-2-carboxylate, glibenclamide, and anti-CFTR antibodies. The absence of CFTR-mediated electrodiffusional ATP movement may thus be a relevant component of the pleiotropic cystic fibrosis phenotype.

scholarly journals Multiple conductance states of the light-activated channel of Limulus ventral photoreceptors. Alteration of conductance state during light.

1991 ◽  
Vol 97 (6) ◽  
pp. 1187-1205 ◽  
Author(s):  
E C Johnson ◽  
J Bacigalupo ◽  
C Vergara ◽  
J E Lisman
Keyword(s):  
Light Adaptation ◽  
Single Channel ◽  
Reversal Potential ◽  
Relative Contribution ◽  
Open Time ◽  
Secondary Result ◽  
The Mean ◽  
Conductance States ◽  
Multiple Conductance States ◽  
Conductance State

The properties of light-dependent channels in Limulus ventral photoreceptors have been studied in cell-attached patches. Two sizes of single-channel events are seen during illumination. Previous work has characterized the large (40 pS) events; the goal of the current work was to characterize the small (15 pS) events and determine their relationship to the large events. The small events are activated by light rather than as a secondary result of the change in membrane voltage during light. The mean open time of the small events is 1.34 +/- 0.49 ms (mean +/- SD, n = 15), approximately 50% of that of the large events. The large and small events have the same reversal potential and a similar dependence of open-state probability on voltage. Evidence that these events are due to different conductance states of the same channel comes from analysis of relatively infrequent events showing a direct transition between the 15 and 40-pS levels. Furthermore, large and small events do not superpose, even at positive voltages when the probability of being open is very high, as would be predicted if the two-sized events were due to independent channels. Expression of the different conductance states is not random; during steady illumination there are alternating periods of several hundred milliseconds in which there are consecutive, sequential large events followed by periods in which there are consecutive, sequential small events. At early times during the response to a step of light, the large conductance state is preferentially expressed. At later times, there is an increase in the relative contribution of the low conductance state. These findings indicate that there is a process that changes the preferred conductance state of the channel. This alteration has functional importance in the process of light adaptation.

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