Characterisation of Binding Sites for δ-Dendrotoxin in Guinea-Pig Synaptosomes: Relationship to Acceptors for the K+-Channel Probe α-Dendrotoxin

Abstract: With use of biologically active 125I-labelled δ-dendrotoxin, a putative K+-channel ligand, homogeneous, noninteracting, high-affinity acceptors (KD= 0.32 ± 0.07 nM; Bmax= 0.33 ± 0.04 pmol/mg) were observed in synaptosomes from guinea-pig cortex. This binding was antagonised noncompetitivel...
Ausführliche Beschreibung

Abstract: With use of biologically active 125I-labelled δ-dendrotoxin, a putative K+-channel ligand, homogeneous, noninteracting, high-affinity acceptors (KD= 0.32 ± 0.07 nM; Bmax= 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. Ausführliche Beschreibung