Practice question

After fusion membrane-embedded SNARE complex ends up as cis-complex where all helices reside in same membrane representing dead-end product incapable of further fusion blocking availability. To maintain flux complex must be disassembled into monomers. Alpha-SNAP adaptor family including alpha, beta, gamma isoforms binds along four-helix bundle recognizing charge pattern; up to four molecules coat complex serving landing pad for hexameric NSF ATPase. NSF contains N-terminal substrate binding domains, D1 ATPase providing mechanical power and D2 stabilizing hexamer. ATP hydrolysis in D1 hydrolyzing up to six ATP per disassembly induces large threading movements as central pore tyrosine grips SNARE pulling through channel analogous to AAA unfoldase. Released SNAREs sort: v-SNARE synaptobrevin packaged into retrograde vesicles for return to donor, t-SNAREs syntaxin and SNAP-25 remain for next round. Dynamin mediates scission using GTP via collar, clathrin heavy chain and AP2 mu mediate sorting, but only NSF ATPase supplies disassembly energy. Alkylation by N-ethylmaleimide inactivates NSF causing rapid accumulation cis-SNARE particles and secretory block within minutes indicating essential recycling role.