A Model Of The Three‐Dimensional Structure Of Snake Venom Neurotoxins Based On Chemical Evidence

Abstract

Data, from studies of covalent structure and chemical and physico‐chemical behaviour of 27 different homologous proteins with either neurotoxic, cardiotoxic or fytic activity isolated from the venoms of elapid or hydrophid snakes have been collected from the literature. Because of their small size (60–74 amino acid residues) and their high content of disulphide bridges (4 or 5 bridges) these proteins provide an unusually favourable opportunity for trials to construct models of three‐dimensional structure from indirect chemical evidence. Such a model has been built from atomic skeleton model units for the Naja nigricollis a‐toxin, which contains 61 amino acid residues and 4 disulfide bridges. The dizerences in amino acid sequences bet ween the proteins with neurotoxic and those with cardiotoxic or lytic activity have been used to assign certain residues as important for the general folding of the molecule and others as important for neurotoxic activity. The last‐mentioned residues are presumed to form the site that binds to the acetyl‐choline receptor.