UT841 purified from sea urchin (Toxopneustes pileolus) venom inhibits time-dependent Ca-45(2+) uptake in crude synaptosome fraction from chick brain

To clarify the mechanism by which the toxic abstract from Toxopneustes pile olus inhibits time-dependent (Time -dep.) Ca2+ uptake in crude synaptosome fraction, the effective component from pedicellarial venom of the yea urchi n was purified. The crude extracts were purified by a series of steps inclu ding. ion exchange (DEAE-sephadex-A25 gel), gel filtration (with Superdex-2 000 and Superdex-peptide columns) and reversed-phase chromatography (Sephas il-C18 column). The effective component that inhibited Time-dep. Ca-45(2+) uptake was purified and named UT841. Its IC50 was determined to be lower th an 35 ng/ml. UT841 is an acidic protein with an apparent molecular weight o f about 18,000. The N-terminal sequence ( 40 amino acids) was almost identi cal to that of Contractin A (a protein purified from the same kind of venom which induces smooth muscle contraction). Even though it is unclear whethe r or not UT841 is Contractin A. Ca2+ 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 selecti vely inhibit Time-dep. Ca-45(2+) uptake. These results suggest that UT841 p urified from sea urchin venom may affect Time-dep. Ca-45(2+) uptake through the metabolism of some lipids and nitric oxide. (C) 2001 Elsevier Science Ltd. All rights reserved.