- A Calcium ions alone, requiring little additional dedicated protein fusion machinery at the presynaptic membrane region as frequently described
- B SNARE proteins (synaptobrevin on vesicle, syntaxin and SNAP-25 on plasma membrane) forming a complex when Ca2+ triggers synaptotagmin
- C ATP hydrolysis alone, occurring largely independent of any incoming calcium signal at the synaptic terminal in most textbook accounts
- D Calmodulin protein acting largely alone, without much involvement of a SNARE protein complex at the membrane during normal conditions
Correct answer: B. SNARE proteins (synaptobrevin on vesicle, syntaxin and SNAP-25 on plasma membrane) forming a complex when Ca2+ triggers synaptotagmin
Explanation: SNARE complex: v-SNARE (synaptobrevin/VAMP) on vesicle + t-SNAREs (syntaxin, SNAP-25) on plasma membrane zip together. Ca2+ sensor synaptotagmin triggers membrane fusion and neurotransmitter release.
Concept context
Brain, spinal cord, neurons, reflex arcs, and sense organs.