Potassium toxin binding site

Voltage-gated potassium channels also have a number of different binding sites. Similar to sodium channels, there is a binding site for peptide toxins at the outer vestibule of the pore. This binding site has been identified by site-directed mutagenesis for different peptide toxins, e.g., for the toxin ShK from a sea anemone, which blocks Kvl.3, or for Charybdotoxin, which blocks various potassium channels [19, 20],... 

The physiological effects of FC are manifold and well documented [16]. Most, if not all of them can be seen in conjunction with the marked acidification of the extracellular space and the hyperpolarization of the membrane potential observed almost immediately after addition of the toxin [16]. Drastic changes in solute transport across the plasma membrane occur (e.g. the potassium uptake by guard cells is stimulated [11]) concomitant with (as a consequence of ) the FC-induced increase in proton motive force. High-affinity FC-binding sites were characterized several years ago [for review see 2] in membranes from a number of plants, but purification of the sites proved impossible. As a consequence perhaps, interest in the binding sites faded after 1982, but has now resumed in several laboratories and this has resulted in the recent identification of the presumptive binding protein as well as its partial purification. 

---