| Autor: |
Doorty, Kevina B., Bevan, Stuart, Wadsworth, Jonathan D.F., Strong, Peter N. |
| Zdroj: |
Journal of Biological Chemistry; August 1997, Vol. 272 Issue: 32 p19925-19930, 6p |
| Abstrakt: |
Taicatoxin, isolated from the venom of the Australian taipan snake Oxyuranus scutellatus, has been previously regarded as a specific blocker of high threshold Ca2+channels in heart. Here we show that taicatoxin (in contrast to a range of other Ca2+channel blockers) interacts with apamin-sensitive, small conductance, Ca2+-activated potassium channels on both chromaffin cells and in the brain. Taicatoxin displays high affinity recognition of125I-apamin acceptor-binding sites, present on rat synaptosomal membranes (Ki= 1.45 ± 0.22 nm) and also specifically blocks affinity-labeling of a 33-kDa 125I-apamin-binding polypeptide on rat brain membranes. Taicatoxin (50 nm) completely blocks apamin-sensitive after-hyperpolarizing slow tail K+currents generated in rat chromaffin cells (mean block 97 ± 3%,n= 12) while only partially reducing total voltage-dependent Ca2+currents (mean block 12 ± 4%, n= 6). In view of these findings, the use of taicatoxin as a specific ligand for Ca2+channels should now be reconsidered. |
| Databáze: |
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