To clarify the mechanism by which the toxic abstract from Toxopneustes pileolus inhibits time-dependent (Time-dep.) Ca(2+) uptake in crude synaptosome fraction, the effective component from pedicellarial venom of the sea urchin was purified. The crude extracts were purified by a series of steps including ion exchange (DEAE-sephadex-A25 gel), gel filtration (with Superdex-2000 and Superdex-peptide columns) and reversed-phase chromatography (Sephasil-C18 column). The effective component that inhibited Time-dep. 45Ca(2+) uptake was purified and named UT841. Its IC(50) was determined to be lower than 35ng/ml. UT841 is an acidic protein with an apparent molecular weight of about 18,000. The N-terminal sequence (40 amino acids) was almost identical to that of Contractin A (a protein purified from the same kind of venom which induces smooth muscle contraction). Even though it is unclear whether or not UT841 is Contractin A, Ca(2+) mobilization in nerve cells was shown to be influenced by UT841. This investigation also revealed that a donor of nitric oxide, arachidonic acid and an inhibitor of phospholipase C selectively inhibit Time-dep. (45)Ca(2+) uptake. These results suggest that UT841 purified from sea urchin venom may affect Time-dep. (45)Ca(2+) uptake through the metabolism of some lipids and nitric oxide.