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| Names | |
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| IUPAC name L-threonyl-L-phenylalanyl-L-isoleucyl-L-alpha-aspartyl-L-valyl-L-alpha-aspartyl-L-cysteinyl-L-threonyl-L-valyl-L-seryl-L-lysyl-L-alpha-glutamyl-L-cysteinyl-L-tryptophyl-L-alanyl-L-prolyl-L-cysteinyl-L-lysyl-L-alanyl-L-alanyl-L-phenylalanyl-glycyl-L-valyl-L-alpha-aspartyl-L-arginyl-glycyl-L-lysyl-L-cysteinyl-L-methionyl-glycyl-L-lysyl-L-lysyl-L-cysteinyl-L-lysyl-L-cysteinyl-L-tyrosyl-L-valine (7->28),(13->33),(17->35)-tris(disulfide) | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| Properties | |
| C177H281N47O50S7 | |
| Molar mass | 4091.86 g/mol |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Slotoxin is apeptide fromCentruroides noxius Hoffmannscorpion venom. It belongs to the short scorpiontoxin superfamily.
For isolation of slotoxin, scorpions of the speciesCentruroides noxius are milked for venom in the laboratory. The crude venom is being dissolved in distilled water and spun. Thesupernatant is separated. The active fraction is then further separated.
The 37amino acid peptide belongs to thecharybdotoxin sub-family (αKTx1) and was numbered member 11. αKTx1.11 revealed specificity for mammalian MaxiK channels (hSlo), thus, was named slotoxin. Its sequence is H-Thr-Phe-Ile-Asp-Val-Asp-Cys(1)-Thr-Val-Ser-Lys-Glu-Cys(2)-Trp-Ala-Pro-Cys(3)-Lys-Ala-Ala-Phe-Gly-Val-Asp-Arg-Gly-Lys-Cys(1)-Met-Gly-Lys-Lys-Cys(2)-Lys-Cys(3)-Tyr-Val-OH.
Slotoxin reversibly blocks the high conductance calcium-activatedpotassium channels composed of only α-subunits (Kd = 1.5 nM). Unreversibly blocks the high conductance calcium-activated potassium channels composed of α- and β1-subunits. Unreversibly and weakly blocks the high conductance calcium-activated potassium channels composed of α- and β4-subunits. It shows no activity on other potassium channels.
The positively charged surface (C-terminal) of SloTx has a specific short-range interaction with the negatively charged pore region of potassium-channels leading to channel blockade. Specifichydrophobic residue-residue interactions between SloTx and MaxiK channels may also contribute to toxin-channel interaction. Another region in the potassium channel (flanking theN-terminal of SloTx) is situated in the face opposite to the site of toxin-pore interaction, and might have implications for the modulation of channel blockade by the MaxiK β subunits.SloTx is suggested to interact with the MaxiK channel pore-forming α-subunitby blocking the pore via a bimolecular reaction.
The large-conductance voltage and calcium-activated potassium (MaxiK, BK) channels are intrinsicmembrane proteins that regulate excitability in a large variety of tissues including brain andsmooth muscle.
