Guangxitoxin 1E, Selective blocker of Kv2.1 and Kv2.2 Guangxitoxin-1E (GxTx-1E) was isolated from the venom of Chilobrachys jingzhao (Chinese earth tiger tarantula). Guangxitoxin-1E was shown to block Kv2.1/KCNB1, Kv2.2/KCNB2 and Kv4.3/KCND3 channels without significant effect on Kv1.2/KCNA2, Kv1.3/KCNA3, Kv1.5/KCNA5, Kv3.2/KCNC2, Cav1.2/CACNA1C, Cav2.2/CACNA1B, Nav1.5/SCN5A, Nav1.7/SCN9A or Nav1.8/SCN10A channels. Guangxitoxin-1E inhibits Kv2.1 with an IC50 value of 1 nM and Kv2.2 with an IC50 value of 3 nM. Block of Kv4.3 occurs at 10-20 fold higher concentrations. Guangxitoxin-1E acts as a gating modifier since it shifts the voltage-dependence of Kv2.1 K+ currents towards depolarized potentials. In pancreatic beta-cells, Guangxitoxin-1E enhances glucose-stimulated insulin secretion by broadening the cell action potential and enhancing calcium oscillations. Guangxitoxin-1E technical information AA sequence: Glu-Gly-Glu-Cys4-Gly-Gly-Phe-Trp-Trp-Lys-Cys11-Gly-Ser-Gly-Lys-Pro-Ala-Cys18-Cys19-Pro-Lys-Tyr-Val-Cys24-Ser-Pro-Lys-Trp-Gly-Leu-Cys31-Asn-Phe-Pro-Met-Pro-OH Presumed disulfide bridge pattern: Cys4-Cys19, Cys11-Cys24 and Cys18-Cys31 Length (aa): 36 Formula: C178H248N44O45S7 Molecular Weight: 3948.70 Da Appearance: White lyophilized solid Solubility: water and saline buffer CAS number: not available Source: Synthetic Purity rate: > 95% http://www.smartox-biotech.com/en/potassium-channel/162-guangxitoxin-1e

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