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Structure. 2003 Nov;11(11):1381-92.

Structural basis of the KcsA K(+) channel and agitoxin2 pore-blocking toxin interaction by using the transferred cross-saturation method.

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Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan.


We have determined the binding site on agitoxin2 (AgTx2) to the KcsA K(+) channel by a transferred cross-saturation (TCS) experiment. The residues significantly affected in the TCS experiments formed a contiguous surface on AgTx2, and substitutions of the surface residues decreased the binding affinity to the KcsA K(+) channel. Based on properties of the AgTx2 binding site with the KcsA K(+) channel, we present a surface motif that is observed in pore-blocking toxins affecting the K(+) channel. Furthermore, we also explain the structural basis of the specificity of the K(+) channel to the toxins. The TCS method utilized here is applicable not only for the channels, which are complexed with other inhibitors, but also with a variety of regulatory molecules, and provides important information about their interface in solution.

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