Preparation of a toxic derivative of sea anemone toxin II from Anemonia sulcata which has peroxidase activity.

Sea anemone toxin II (ATX II) is a useful tool for investigation of sodium channels in excitable membranes. Coupling of ATX II with microperoxidase, a heme-octapeptide, is described. The isolated cross-linked product possesses both toxic and peroxidase activity. The lowest concentration of the modified toxin that affects the action potential and the membrane currents in single cardiac myocytes is 16 nM. The enzymatically active ATX II derivative may be useful for biochemical applications and as a non-radioactive tracer for electron microscopy studies of excitable tissue.