Effects of venom from Conus striatus on the delayed rectifier potassium current of molluscan neurons

Potassium channel toxins

Many venom toxins interfere with ion channel function. Toxins, as specific, high affinity ligands, have played an important part in purifying and characterizing many ion channel proteins. Our knowledge of potassium ion channel structure is meager because until recently, no specific potassium channel toxins were known, or identified as such. This review summarizes the sudden explosion of research on potassium channel toxins that has occurred in recent years. Toxins are discussed in terms of their structure, physiological and pharmacological properties, and the characterization of toxin binding sites on different subtypes of potassium ion channels.

Toxins in the characterization of potassium channels

Several recently characterized toxins (apamin, charybdotoxin, dendrotoxin and noxiustoxin) are proving invaluable for establishing what kinds of potassium channel are expressed in neurones, and what the roles of the channels might be.

An emerging pharmacology of peptide toxins targeted against potassium channels

Voltage-dependent ion channels are a difficult class of proteins to approach biochemically. Many such channels are present at low density in relevant tissues and exist as multiple subtypes that can be distinguished electrophysiologically. In particular, K channels appear to be a diverse family of proteins characterized by many different conductance properties, gating behaviors and regulatory phenomena. Fortunately, specific peptide toxins for K channels are present in the venoms of insects, scorpions, snakes and possibly other species. The available sequences of these peptides define several different families of toxins. Electrophysiological and radioligand binding studies suggest that these toxins can be used to distinguish subclasses of K channels that share similar toxin binding sites. The growing databank of sequence homologies for both toxins and channels is, in essence, a codebook for identifying common elements of structure and function. The continuing development of toxins as biochemical probes should help to uncover the molecular basis and physiological significance of K-channel diversity.