Practice question

Alpha-SNAP soluble attachment protein family 35 kDa containing N-terminal helical bundle and C-terminal tetratricopeptide repeats serving adaptor for NSF ATPase. After fusion four-helix cis-SNARE complex remains tightly intertwined embedded in acceptor membrane extremely stable. Alpha-SNAP tetramer binds along outer surface grooves via charged interactions each molecule providing C-terminal leucine repeat interface for one N-domain of hexameric NSF oligomer. Once six N-domains engage four SNAPs 20S supercomplex forms stabilized by ATP bound non-hydrolyzable state where SNAP orientation presents SNAREs to central pore. Upon ATP binding then hydrolysis in D1 ring pore loops containing conserved aromatic residues exert pulling force threading SNARE polypeptide through central channel unfolding coiled coil into monomers recycling syntaxin retained and VAMP for retrograde trafficking. Alpha-SNAP couples NSF ATPase to SNARE disassembly. Mitochondrial import uses separate TIM/TOM PAM motors, Rab docking uses effector tethers EEA1, degradation not normal fate. In vitro purified alpha-SNAP plus NSF plus ATP sufficient to disassemble neuronal SNAREs demonstrating dedicated role as SNARE recycling chaperone after membrane fusion events.