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From Proteopedia
Solution structure of HERG-specific scorpion toxin BeKm-1
Structural highlights
FunctionKGX21_MESEU Blocks human and/or rat Kv11.1/KCNH2/ERG1, Kv11.2/KCNH6/ERG2 and Kv11.3/KCNH7/ERG3 by binding to channel outer vestibule (S5P domain) with a 1:1 stoichiometry. Inhibition data are the following: hERG1 (reversible, Kd=7.7 nM (PubMed:16497878), IC(50)=3.3 nM (PubMed:11136720), IC(50)=11.9 nM (PubMed:21205913)), rERG1 (reversible, Kd=19 nM) (PubMed:16497878), hERG2 (reversible, Kd=77 nM) (PubMed:16497878), rERG2 (irreversible, Kd=4.2 nM) (PubMed:16497878), hERG3 (reversible, Kd=11.5 nM) (PubMed:16497878) and rERG3 (reversible, Kd=747 nM) (PubMed:16497878) potassium channels. Has also a minimal effect on rat ELK1/KCNH4 potassium channels (9% inhibition at 100 nM (PubMed:15137031)). Both this toxin and CnErgTx1 (AC Q86QT3) share mechanism of action and have overlapping binding sites on ERG1 (PubMed:12719233). The potency of these two toxins is not affected by elevating potassium ion concentration from 2 to 98 mM (PubMed:12719233). In addition, at high toxin concentrations, block of ERG1 macroscopic currents by these two toxins is incomplete (88%) (PubMed:12719233). The blockade by this toxin is preferentially closed channel state-dependent, with a component of open, but not inactive state-dependent blockade (PubMed:12860380). This toxin produces a concentration-dependent prolongation of QTc in the isolated rabbit heart (16.3% at 100 nM) (PubMed:21205913).[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedThe scorpion toxin BeKm-1 is unique among a variety of known short scorpion toxins affecting potassium channels in its selective action on ether-a-go-go-related gene (ERG)-type channels. BeKm-1 shares the common molecular scaffold with other short scorpion toxins. The toxin spatial structure resolved by NMR consists of a short alpha-helix and a triple-stranded antiparallel beta-sheet. By toxin mutagenesis study we identified the residues that are important for the binding of BeKm-1 to the human ERG K+ (HERG) channel. The most critical residues (Tyr-11, Lys-18, Arg-20, Lys-23) are located in the alpha-helix and following loop whereas the "traditional" functional site of other short scorpion toxins is formed by residues from the beta-sheet. Thus the unique location of the binding site of BeKm-1 provides its specificity toward the HERG channel. New binding site on common molecular scaffold provides HERG channel specificity of scorpion toxin BeKm-1.,Korolkova YV, Bocharov EV, Angelo K, Maslennikov IV, Grinenko OV, Lipkin AV, Nosyreva ED, Pluzhnikov KA, Olesen SP, Arseniev AS, Grishin EV J Biol Chem. 2002 Nov 8;277(45):43104-9. Epub 2002 Jul 31. PMID:12151390[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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