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Characterisation of Binding Sites for δ‐Dendrotoxin in Guinea‐Pig Synaptosomes: Relationship to Acceptors for the K + ‐Channel Probe α‐Dendrotoxin
Author(s) -
Muniz Zilda M.,
Diniz Carlos R.,
Dolly J. Oliver
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb13320.x
Subject(s) - chemistry , membrane , synaptosome , biophysics , guinea pig , binding site , ligand (biochemistry) , stereochemistry , receptor , biochemistry , biology , endocrinology
With use of biologically active 125 I‐labelled δ‐dendrotoxin, a putative K + ‐channel ligand, homogeneous, noninteracting, high‐affinity acceptors ( K D = 0.32 ± 0.07 n M ; B max = 0.33 ± 0.04 pmol/mg) were observed in synaptosomes from guinea‐pig cortex. This binding was antagonised noncompetitively by α‐dendrotoxin, an inhibitor of certain fast‐activating, voltage‐gated K + channels. Chemical cross‐linking of the δ‐dendrotoxin‐acceptor complex in synaptosomes yielded two specifically labeled polypeptides with molecular masses of 69 and 82 kilodaltons. Although α‐dendrotoxin prevents the labelling of both these bands, it cross‐linked only a single protein with a molecular mass of 69 kilodaltons. It is concluded that δ‐dendrotoxin interacts with a distinct site on the oligomeric acceptors for α‐dendrotoxin.