Accession Number : ADA254629
Title : Site-Specific Antagonists to Tetrodotoxin and Saxitoxin.
Descriptive Note : Final rept. 1 Apr 87-31 Mar 92,
Corporate Author : STATE UNIV OF NEW YORK AT BROOKLYN
Personal Author(s) : Kao, C Y
Report Date : 01 May 1992
Pagination or Media Count : 24
Abstract : Tetrodotoxin (TTX) and saxitoxin (STX) are important neurobiological tools because of their unique high-specificity and high-potency blockade of voltage-gated sodium channels. Although chemically different, their actions are identical. The biophysical mechanism of their actions have been exhaustively studied, but the chemical nature of the actions remains unknown. By studying the structure-activity relations of some natural and synthetic analogues of both TTX and STX on the voltage-clamped frog skeletal muscle fiber, we have deduced that the TTX/STX binding site is a pocket 9.5 angstrom (width) x 6 angstrom (height) and 5 angstrom (depth), located in a fold of the sodium-channel protein, close to the external orifice. There are 7 anchoring sites, a - g, which ion-pairs or hydrogen-bonds with surface groups in the toxinmolecules. TTX and STX share one ion-pairing and 4 H-bonding sites in common. Such a binding site also explains the actions of the TTX analogue, chiriquitoxin, and SSTX analogues, gonyautoxins and sulfocarbamoyl saxitoxins. A specifically labelled HTTX of 2900 Ci/mol has been synthesized for use in continuing efforts to locate the binding site.
Descriptors : *TOXICITY , *NEUROPHYSIOLOGY , *MUSCLE FIBERS , *NEUROCHEMICAL TRANSMISSION , IONS , FIBERS , HYDROGEN BONDS , PROTEINS , STRUCTURES , VOLTAGE , HYDROGEN , BONDING , ORIFICES , POTENCY , FROGS , CHANNELS , HEIGHT , MUSCLES , EXTERNAL , SURFACES , DEPTH , SODIUM , SITES , TOOLS , CHEMICALS , MOLECULES
Subject Categories : Biology
Distribution Statement : APPROVED FOR PUBLIC RELEASE