Himehabu lectin, a novel inducer of Ca2+-release from the venom of the snake Trimeresurus okinavensis, in sarcoplasmic reticulum

The lectin himehabu lectin (HHL) has recently been isolated from crude veno m of the snake Trimeresurus okinavensis. Ca2+-electrode and fluorescent Ca2+-indicator experiments showed that HHL i nduced release of Ca2+ from the heavy fraction of skeletal muscle sarcoplas mic reticulum (HSR). The release of Ca2+ induced by caffeine from HSR was a bolished by ryanodine, Mg2+ and ruthenium red, typical inhibitors of Ca2+-r elease channels, whereas that induced by HHL was only partially reduced by these inhibitors. HHL, unlike caffeine, had no effect on [H-3]ryanodine bin ding to HSR. These results suggest that HHL induces release of Ca2+ which is at least pa rtially mediated through Ca2+-release channels with novel pharmacological p roperties.