Partial Characterization of a Tetrodotoxin-Binding Component from Nerve Membrane

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Abstract
Tetrodotoxin from Japanese puffer fish has been labeled with tritium and purified from the crude mixture obtained. The interaction between the purified [(3)H]tetrodotoxin and membrane suspensions from the olfactory nerve of long-nosed garfish has been investigated by equilibrium dialysis. Tetrodotoxin binds to membrane suspensions with a dissociation constant K(D) = 8.3 nM. The nerve preparation binds 42 pmol of [(3)H]tetrodotoxin/g of wet tissue at saturating toxin concentrations. With various hydrolytic enzymes, the binding component is shown to be a protein embedded in a phospholipid environment. The binding is inhibited below pH 4.0 and is not stable towards heat. Tetrodotoxin binding is not inhibited by the local anesthetic, procaine.