Interactions within the yeast t-SNARE Sso1p that control SNARE complex assembly.

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Intracellular trafficking relies on transport vesicles fusing with target membranes.
• SNARE protein complexes mediate vesicle fusion.
• Syntaxin proteins, including yeast Sso1p, adopt a closed conformation that inhibits SNARE assembly.

Purpose of the Study:

• To visualize the closed conformation of yeast syntaxin (Sso1p) directly.
• To investigate how this conformation regulates SNARE complex assembly.
• To understand the mechanisms controlling intracellular trafficking.

Main Methods:

• X-ray crystallography was used to determine the structure of yeast Sso1p.
• Site-directed mutagenesis was employed to create mutants destabilizing the closed conformation.
• In vitro assays measured the rates of SNARE assembly.

Main Results:

• The X-ray crystal structure of yeast Sso1p in its closed conformation was determined to 2.1 A resolution.
• Mutants designed to destabilize the closed conformation showed faster SNARE assembly rates.
• These findings provide direct visualization of the inhibitory conformation.

Conclusions:

• The closed conformation of syntaxins plays a critical role in regulating SNARE assembly.
• Destabilizing this conformation enhances SNARE complex formation.
• This study offers insights into the intramolecular and intermolecular regulation of intracellular transport.