Linked Life Data

2480347

Source:http://linkedlifedata.com/resource/pubmed/id/2480347

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
35
pubmed:dateCreated
1990-1-19
pubmed:abstractText
Charybdotoxin (ChTX), a peptidyl inhibitor of the high conductance Ca2+-activated K+ channel (PK,Ca), has been radiolabeled to high specific activity with 125I, and resulting derivatives have been well separated. The monoiodotyrosine adduct blocks PK,Ca in vascular smooth muscle with slightly reduced potency compared with the native peptide under defined experimental conditions. [125I]ChTX, representing this derivative, binds specifically and reversibly to a single class of sites in sarcolemmal membrane vesicles prepared from bovine aortic smooth muscle. These sites display a Kd of 100 pM for the iodinated toxin, as determined by either equilibrium or kinetic binding analyses. Binding site density is about 500 fmol/mg of protein in isolated membranes. The addition of low digitonin concentrations to disrupt the vesicle permeability barrier increases the maximum receptor concentration to 1.5 pmol/mg of protein, correlating with the observations that ChTX binds only at the external pore of PK,Ca and that the membrane preparation is of mixed polarity. Competition studies with ChTX yield a Ki of about 20 pM for native toxin. Binding of [125I]ChTX is modulated by ionic strength as well as by metal ions that are known to interact with PK,Ca. Moreover, tetraethylammonium ion, which blocks PK,Ca with moderately high affinity when applied at the external membrane surface, inhibits [125I]ChTX binding in an apparently competitive fashion with a Ki similar to that found for channel inhibition. In marked contrast, agents that do not inhibit PK,Ca in smooth muscle (e.g. tetrabutylammonium ion, other toxins homologous with ChTX, and pharmacological agents that modulate the activity of dissimilar ion channels) have no effect on [125I]ChTX binding in this tissue. Taken together, these results suggest that the binding sites for ChTX which are present in vascular smooth muscle are directly associated with PK,Ca, thus identifying [125I]ChTX as a useful probe for elucidating the biochemical properties of these channels.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
264
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
20902-9
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
Characterization of high affinity binding sites for charybdotoxin in sarcolemmal membranes from bovine aortic smooth muscle. Evidence for a direct association with the high conductance calcium-activated potassium channel.
pubmed:affiliation
Department of Membrane Biochemistry and Biophysics, Merck Institute for Therapeutic Research, New Jersey 07065.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, Non-P.H.S.