title: BTK-2, a new inhibitor of the Kv1.1 potassium channel purified from Indian scorpion Buthus tamulus.
abstract: A novel inhibitor of voltage-gated potassium channel was isolated and purified to homogeneity from the venom of the red scorpion Buthus tamulus. The primary sequence of this toxin, named BTK-2, as determined by peptide sequencing shows that it has 32 amino acid residues with six conserved cysteines. The molecular weight of the toxin was found to be 3452 Da. It was found to block the human potassium channel hKv1.1 (IC(50)=4.6 microM). BTK-2 shows 40-70% sequence similarity to the family of the short-chain toxins that specifically block potassium channels. Multiple sequence alignment helps to categorize the toxin in the ninth subfamily of the K+ channel blockers. The modeled structure of BTK-2 shows an alpha/beta scaffold similar to those of the other short scorpion toxins. Comparative analysis of the structure with those of the other toxins helps to identify the possible structure-function relationship that leads to the difference in the specificity of BTK-2 from that of the other scorpion toxins. The toxin can also be used to study the assembly of the hKv1.1 channel.
authors.affiliation: Biomembrane Research Lab, Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Dhawan
authors.forename: Anurag
authors.initials: A
authors.lastname: Varshney
authors.forename: M K
authors.initials: MK
authors.lastname: Mathew
authors.forename: Anil K
authors.initials: AK
authors.lastname: Lala
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051662:Kv1.1 Potassium Channel; D008969:Molecular Sequence Data; D026902:Potassium Channel Blockers / Q000302:isolation & purification*; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms / Q000737:chemistry*; D012605:Scorpions; D017386:Sequence Homology, Amino Acid
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms; D051662:Kv1.1 Potassium Channel