Linked Life Data

1379069

Source:http://linkedlifedata.com/resource/pubmed/id/1379069

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
29
pubmed:dateCreated
1992-8-28
pubmed:abstractText
The interaction of iberiotoxin (IbTX) with the large-conductance calcium-activated potassium (maxi-K) channel was examined by measuring single-channel currents from maxi-K channels incorporated into planar lipid bilayers. Addition of nanomolar concentrations of IbTX to the external side of the channel produced long nonconducting silent periods, which were interrupted by periods of normal channel activity. The distributions of durations of blocked and unblocked periods were both described by single exponentials. The mean duration of the unblocked periods decreased in proportion with the external concentration of IbTX, while the mean duration of the blocked periods was not affected. These results suggest that IbTX blocks the maxi-K channel through a simple bimolecular binding reaction where the silent periods represent times when a single toxin molecule is bound to the channel. In symmetric solutions of 150 mM KCl, with a membrane potential of 40 mV, the mean duration of the blocked periods produced by IbTX was 840 s, and the association rate was 1.3 x 10(6) M-1 s-1, yielding an equilibrium dissociation constant of about 1 nM. Raising the internal potassium concentration increased the dissociation rate constant of IbTX in a manner which was well described by a saturable binding function for potassium. External tetraethylammonium ion increased the average duration of the unblocked periods without affecting the blocked periods, suggesting that tetraethylammonium and IbTX compete for the same site near the conductance pathway of the channel. Increasing the external concentration of monovalent cations from 25 to 300 mM with either potassium or sodium decreased the rate of binding of IbTX to the channel by approximately 24-fold, with little effect on the rate of toxin dissociation.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
28
pubmed:volume
31
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6719-27
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:1379069-Amino Acid Sequence, pubmed-meshheading:1379069-Animals, pubmed-meshheading:1379069-Aorta, pubmed-meshheading:1379069-Calcium, pubmed-meshheading:1379069-Cattle, pubmed-meshheading:1379069-Cells, Cultured, pubmed-meshheading:1379069-Charybdotoxin, pubmed-meshheading:1379069-Kinetics, pubmed-meshheading:1379069-Lipid Bilayers, pubmed-meshheading:1379069-Mathematics, pubmed-meshheading:1379069-Membrane Fusion, pubmed-meshheading:1379069-Membrane Potentials, pubmed-meshheading:1379069-Models, Biological, pubmed-meshheading:1379069-Molecular Sequence Data, pubmed-meshheading:1379069-Muscle, Smooth, Vascular, pubmed-meshheading:1379069-Peptides, pubmed-meshheading:1379069-Potassium Channels, pubmed-meshheading:1379069-Sarcolemma, pubmed-meshheading:1379069-Scorpion Venoms, pubmed-meshheading:1379069-Sequence Homology, Nucleic Acid
pubmed:year
1992
pubmed:articleTitle
Mechanism of iberiotoxin block of the large-conductance calcium-activated potassium channel from bovine aortic smooth muscle.
pubmed:affiliation
Department of Membrane Biochemistry and Biophysics, Merck Institute for Therapeutic Research, Rahway, New Jersey 07065.
pubmed:publicationType
Journal Article, Comparative Study