PT  - JOURNAL ARTICLE
AU  - Violeta Visan
AU  - Ziad Fajloun
AU  - Jean-Marc Sabatier
AU  - Stephan Grissmer
TI  - Mapping of Maurotoxin Binding Sites on hKv1.2, hKv1.3, and hIKCa1 Channels
AID  - 10.1124/mol.104.002774
DP  - 2004 Nov 01
TA  - Molecular Pharmacology
PG  - 1103--1112
VI  - 66
IP  - 5
4099  - http://molpharm.aspetjournals.org/content/66/5/1103.short
4100  - http://molpharm.aspetjournals.org/content/66/5/1103.full
SO  - Mol Pharmacol2004 Nov 01; 66
AB  - Maurotoxin (MTX) is a potent blocker of human voltage-activated Kv1.2 and intermediate-conductance calcium-activated potassium channels, hIKCa1. Because its blocking affinity on both channels is similar, although the pore region of these channels show only few conserved amino acids, we aimed to characterize the binding sites of MTX in these channels. Investigating the pHo dependence of MTX block on current through hKv1.2 channels, we concluded that the block is less pHo - sensitive than for hIKCa1 channels. Using mutant cycle analysis and computer docking, we tried to identify the amino acids through which MTX binds to hKv1.2 and hIKCa1 channels. We report that MTX interacts with hKv1.2 mainly through six strong interactions. Lys23 from MTX protrudes into the channel pore interacting with the GYGD motif, whereas Tyr32 and Lys7 interact with Val381, Asp363, and Glu355, stabilizing the toxin onto the channel pore. Because only Val381, Asp363, and the GYGD motif are conserved in hIKCa1 channels, and the replacement of His399 from hKv1.3 channels with a threonine makes this channel MTX-sensitive, we concluded that MTX binds to all three channels through the same amino acids. Glu355, although important, is not essential in MTX recognition. A negatively charged amino acid in this position could better stabilize the toxin-channel interaction and could explain the pHo sensitivity of MTX block on current through hIKCa1 versus hKv1.2 channels.