[Structure-activity study of the basic toxic component of venom from the ant Ectatomma tuberculatum].

A toxic principle of the Ectatomma tuberculatum ant venom called ectatomin was isolated. Ectatomin is a protein with molecular weight 7928 Da. Its complete amino acid sequence and spatial structure in aqueous solution were determined by protein chemistry methods and NMR spectroscopy techniques. Ectatomin contains two highly homologous polypeptide chains linked to each other by a disulfide bond. The chains consist of 37 and 34 amino acid residues with an internal disulfide bridge in each. In aqueous solution the molecule forms a bundle of four amphipathic alpha-helices. This toxin in a concentration of 0.05-0.01 mM forms potential dependent nonselective cation channels both in cell and artificial membranes. The channel is dimeric and the mechanism of its formation can be explained in terms of the spatial structure established.