Constitutive versus regulated SNARE assembly: a structural basis.
SNARE complex formation is essential for intracellular membrane fusion. Vesicle-associated (v-) SNARE intertwines with target membrane (t-) SNARE to form a coiled coil that bridges two membranes and facilitates fusion. For the SNARE family involved in neuronal communications, complex formation is tightly regulated by the v-SNARE-membrane interactions. However, it was found using EPR that complex formation is spontaneous for a different SNARE family that is involved in protein trafficking in yeast. Further, reconstituted yeast SNAREs promoted membrane fusion, different from the inhibited fusion for reconstituted neuronal SNAREs. The EPR structural analysis showed that none of the coiled-coil residues of yeast v-SNARE is buried in the hydrophobic layer of the membrane, making the entire coiled-coil motif accessible, again different from the deep insertion of the membrane-proximal region of neuronal v-SNARE into the bilayer. Importantly, yeast membrane fusion is constitutively active, while synaptic membrane fusion is regulated, consistent with the present results for two SNARE families. Thus, the v-SNARE-membrane interaction may be a major molecular determinant for regulated versus constitutive membrane fusion in cells.
Chen
Yong
Y
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
Xu
Yibin
Y
Zhang
Fan
F
Shin
Yeon-Kyun
YK
D000595:Amino Acid Sequence; D004578:Electron Spin Resonance Spectroscopy; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D005982:Glutathione Transferase / Q000235:genetics; D008081:Liposomes / Q000737:chemistry; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D050600:SNARE Proteins; D013113:Spin Labels; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology
D005656:Fungal Proteins; D008081:Liposomes; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D013113:Spin Labels; D033921:Vesicular Transport Proteins; D005982:Glutathione Transferase