Unique Structural Features of Membrane-Bound C-Terminal Domain Motifs Modulate Complexin Inhibitory Function

Area of Science:

• Neuroscience
• Molecular Biology
• Biophysics

Background:

• Complexin regulates synaptic vesicle exocytosis by interacting with neuronal SNARE proteins.
• The C-terminal domain (CTD) of complexin is crucial for its inhibitory function in neurotransmitter release.
• The membrane-binding motifs of the CTD are poorly characterized, hindering mechanistic understanding.

Purpose of the Study:

• To define the boundaries and characterize the conformations of the two CTD membrane-binding motifs.
• To elucidate the role of complexin membrane interactions in regulating synaptic function.
• To investigate the structural basis of complexin's inhibitory role in neurotransmission.

Main Methods:

• Optical spectroscopy
• Magnetic resonance spectroscopy
• In vivo functional assays

Main Results:

• Precisely defined the boundaries of the two CTD membrane-binding motifs.
• Characterized the conformations of these membrane-bound motifs.
• Identified an irregular helical structure (pi-bulge) in the curvature-dependent motif, crucial for inhibitory function.

Conclusions:

• The CTD's membrane-binding motifs and their conformations are critical for complexin's inhibitory function.
• A specific structural feature (pi-bulge) in a membrane curvature-dependent motif is essential for inhibiting neurotransmitter release.
• These findings clarify the mechanisms of complexin's role in synaptic transmission.