Synaptic neurotransmitter release is the most critical communication process for the connections between neurons and between neurons and target cells. SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) are believed to be highly involved in docking and fusion of synaptic vesicles to the pre-synaptic plasma membrane. In vivo, synaptic vesicle exocytosis is a regulated and extremely rapid process. Numerous regulatory proteins are also required to achieve the fast speed and Ca2+ dependency of synaptic neurotransmitter release.

Our research mainly focuses on investigating the mechanism and protein structural basis of SNARE mediated membrane fusion. Site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy are powerful tools to study the structure and membrane topology of membrane proteins in lipid bilayer. We use these advanced techniques to probe the structure of SNARE proteins and the important regulators in neurotransmitter release.

Neurotransmitter release takes place on a much shorter time scale compared to other kind of exocytosis and this fast release is accurately coupled with Ca2+ signaling. In this dissertation, we have revealed some structure details that contribute to understand the underlying mechanism of this fine-tuning process. Firstly, the structural analysis of complexin/SNARE complex discloses a balance between different interaction patterns of complexin and SNARE. The exchange of these interaction patterns might switch the complexin function between stimulation and inhibition during different fusion steps. Then we further investigate the linker region structure of SNARE complex in different zippering stages and obtain detailed information about the conformational changes of this linker region during SNARE zippering process. The results we have got from these studies may shed light on the molecular basis of the efficient and precise

control of SNARE machinery on neurontransmitter release.