Polypeptide toxin pi-AnmTX Hcr 1b-1 with a molecular weight 4537 Da was isolated from the whole body extract of sea anemone by a multistage liquid chromatography. The BLAST search algorithm revealed homology of the novel toxin amino acid sequence to the group of the known sea anemone toxins including BDS and APETx with similarity less then 50%. The toxin pi-AnmTX Hcr 1b-1 inhibited the amplitude of the fast component of integral ASIC3 current in electrophysiological studies on receptors expressed in Xenopus laevis oocytes. The calculated IC50 value was 5.5 +/- 1.0 microM. Among the known polypeptide toxins interacted with ASICs channels, the micro-AnmTX Hcr 1b-1 toxin is the least potent inhibitor that in our opinion correlates with a small amount of charged amino acid residues in its structure.