STRUCTURAL AND FUNCTIONAL-STUDIES OF TOXI C PRINCIPLE OF ECTATOMMA-TUBERCULATUM ANT VENOM

A toxic principle of the Ectatomma tuberculatum ant venom called ectat omin was isolated. Ectatomin is a protein with molecular weight 7928 D a. Its complete amino acid sequence and spatial structure in aqueous s olution were determined by protein chemistry methods and NMR spectrosc opy techniques. Ectatomin contains two highly homologous polypeptide c hains linked to each other by a disulfide bond. The chains consist of 37 and 34 amino acid residues with an internal disulfide bridge in eac h. In aqueous solution the molecule forms a bundle of four amphipathic alpha-helices. This toxin in a concentration of 0.05-0.1 mM forms pot ential dependent nonselective cation channels both in cell and artific ial membranes. The channel is dimeric and the mechanism of its formati on can be explained in terms of the spatial structure established.