Bacterial dynamin-like protein DynA mediates lipid and content mixing

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacterial dynamin-like proteins (DLPs) are involved in various cellular processes but their mechanisms remain largely unknown.
• DynA from Bacillus subtilis is a DLP that tethers membranes and contributes to bacterial immunity.
• Understanding bacterial DLP function is crucial for deciphering bacterial innate immunity and membrane dynamics.

Purpose of the Study:

• To investigate if bacterial DLP DynA induces membrane full fusion.
• To characterize the roles of DynA subunits in membrane fusion.
• To explore the involvement of GTP hydrolysis in DynA-mediated fusion, particularly the fusion-through-hemifusion pathway.

Main Methods:

• Lipid and content mixing assays in reconstituted systems.
• Fluorescence resonance energy transfer (FRET) to monitor membrane fusion.
• In vitro assays to study DynA's interaction with membranes and its subunits' functions.

Main Results:

• DynA induces aqueous content mixing and lipid mixing in vitro, independent of GTP.
• DynA-mediated membrane fusion is a slow, thermo-promoted process with preferences for specific phospholipids and membrane curvature.
• The D1 subunit is essential for membrane binding and fusion, while D2 facilitates fusion; DynA disassembly accelerates content exchange.

Conclusions:

• Bacterial DLP DynA acts as a membrane fusion catalyst, distinct from known eukaryotic systems.
• DynA's ability to mediate fusion without a transmembrane domain offers a unique model for membrane fusion.
• DynA disassembly is a key driver for the fusion-through-hemifusion pathway in bacteria.