passages.id: split_6_test_2516_passage
passages.type: progene_text
passages.text: The most extensively studied candidate for the Ca(2+) - sensing trigger is synaptotagmin I , whose Ca(2+) - dependent interactions with acidic phospholipids and syntaxin have largely been ascribed to its C(2) A domain , although the C(2) B domain also binds Ca(2+) ( refs 7 , 8 ) .