-Independent Syntaxin Binding to the C2B Effector Region of Synaptotagmin

Although synaptotagmin I, which is a calcium (Ca 2+)-binding synaptic vesicle protein, may trigger soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated synaptic vesicle exocytosis, the mechanisms underlying the interaction between these proteins remains controversial, especially with respect to the identity of the protein(s) in the SNARE complex that bind(s) to synaptotagmin and whether Ca 2+ is required for their highly effective binding. To address these questions, native proteins were solubilized, 2+-independent 3 fashion, providing biochemical evidence that synaptotagmin I binds SNARE complexes before Ca 2+ influx into presynaptic nerve terminals.