Disassembly of All SNARE Complexes by N-Ethylmaleimide-sensitive Factor (NSF) Is Initiated by a Conserved 1:1 Interaction between α-Soluble NSF Attachment Protein (SNAP) and SNARE Complex*

Abstract

Vesicle trafficking in eukaryotic cells is facilitated by SNARE-mediated membrane fusion. The ATPase NSF (N-ethylmaleimide-sensitive factor) and the adaptor protein α-SNAP (soluble NSF attachment protein) disassemble all SNARE complexes formed throughout different pathways, but the effect of SNARE sequence and domain variation on the poorly understood disassembly mechanism is unknown. By measuring SNARE-stimulated ATP hydrolysis rates, Michaelis-Menten constants for disassembly, and SNAP-SNARE binding constants for four different ternary SNARE complexes and one binary complex, we found a conserved mechanism, not influenced by N-terminal SNARE domains. α-SNAP and the ternary SNARE complex form a 1:1 complex as revealed by multiangle light scattering. We propose a model of NSF-mediated disassembly in which the reaction is initiated by a 1:1 interaction between α-SNAP and the ternary SNARE complex, followed by NSF binding. Subsequent additional α-SNAP binding events may occur as part of a processive disassembly mechanism.Background: NSF and α-SNAP disassemble all SNARE complexes.Results: The disassembly kinetics is conserved for different ternary and binary SNARE complexes. α-SNAP and the ternary SNARE complex form a 1:1 complex.Conclusion: NSF uses a conserved mechanism to disassemble all SNARE complexes, starting from a 1:1 SNAP-SNARE complex interaction.Significance: We illuminate a broad mechanism allowing NSF to support SNARE-mediated exocytosis. Vesicle trafficking in eukaryotic cells is facilitated by SNARE-mediated membrane fusion. The ATPase NSF (N-ethylmaleimide-sensitive factor) and the adaptor protein α-SNAP (soluble NSF attachment protein) disassemble all SNARE complexes formed throughout different pathways, but the effect of SNARE sequence and domain variation on the poorly understood disassembly mechanism is unknown. By measuring SNARE-stimulated ATP hydrolysis rates, Michaelis-Menten constants for disassembly, and SNAP-SNARE binding constants for four different ternary SNARE complexes and one binary complex, we found a conserved mechanism, not influenced by N-terminal SNARE domains. α-SNAP and the ternary SNARE complex form a 1:1 complex as revealed by multiangle light scattering. We propose a model of NSF-mediated disassembly in which the reaction is initiated by a 1:1 interaction between α-SNAP and the ternary SNARE complex, followed by NSF binding. Subsequent additional α-SNAP binding events may occur as part of a processive disassembly mechanism. Background: NSF and α-SNAP disassemble all SNARE complexes. Results: The disassembly kinetics is conserved for different ternary and binary SNARE complexes. α-SNAP and the ternary SNARE complex form a 1:1 complex. Conclusion: NSF uses a conserved mechanism to disassemble all SNARE complexes, starting from a 1:1 SNAP-SNARE complex interaction. Significance: We illuminate a broad mechanism allowing NSF to support SNARE-mediated exocytosis.