1lir
LQ2 FROM LEIURUS QUINQUESTRIATUS, NMR, 22 STRUCTURES
Structural highlights
FunctionKAX12_LEIHE Blocks calcium-activated potassium channels (Kd=43 nM on KCa1.1/KCNMA1). Has a potent presynaptic facilitatory action, with less effect on direct muscle stimulation.[1] [2] Publication Abstract from PubMedLq2 is a unique scorpion toxin. Acting from the extracellular side, Lq2 blocks the ion conduction pore in not only the voltage- and Ca2+ -activated channels, but also the inward-rectifier K+ channels. This finding argues that the three-dimensional structures of the pores in these K+ channels are similar. However, the amino acid sequences that form the external part of the pore are minimally conserved among the various classes of K+ channels. Because Lq2 can bind to all the three classes of K+ channels, we can use Lq2 as a structural probe to examine how the non-conserved pore-forming sequences are arranged in space to form similar pore structures. In the present study, we determined the three-dimensional structure of Lq2 using nuclear magnetic resonance (NMR) techniques. Lq2 consists of an alpha-helix (residues S10 to L20) and a beta-sheet, connected by an alphabeta3 loop (residues N22 to N24). The beta-sheet has two well-defined anti-parallel strands (residues G26 to M29 and residues K32 to C35), which are connected by a type I' beta-turn centered between residues N30 and K31. The N-terminal segment (residues Z1 to T8) appears to form a quasi-third strand of the beta-sheet. Solution structure of potassium channel-inhibiting scorpion toxin Lq2.,Renisio JG, Lu Z, Blanc E, Jin W, Lewis JH, Bornet O, Darbon H Proteins. 1999 Mar 1;34(4):417-26. PMID:10081954[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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