FIGURE 3.

Phosphatidylserine (PS) effector protein synaptotagmin I is involved in neurotransmitter release. As the figure shows, synaptotagmin I possesses two C2 domains to bind Ca²⁺ and PS. N-terminus of synaptotagmin I is in synaptic vesicles and C2 domain in cytoplasmic. Synaptotagmin I binds Ca²⁺ when Ca²⁺ flows into cells from the Ca²⁺ channels. The Ca²⁺ binding further increases the binding of synaptotagmin I to SNARE complex as well as the fusion of synaptic and plasma membrane. SNARE complex includes the synaptosome-associated protein of 25 kDa (SNAP25), synataxin, and synaotobrevin. Created with BioRender.com.