Double-Transmembrane Domain of SNAREs Decelerates the Fusion by Increasing the Protein-Lipid Mismatch

SNARE is the essential mediator of membrane fusion that highly relies on the molecular structure of SNAREs. For instance, the protein syntaxin-1 involved in neuronal SNAREs, has a single transmembrane domain (sTMD) leading to fast fusion, while the syntaxin 17 has a V-shape double TMDs (dTMDs), taking part in the autophagosome maturation. However, it is not clear how the TMD structure influences the fusion process. Here, we demonstrate that the dTMDs significantly reduce fusion rate compared with the sTMD by using an in vitro reconstitution system. Through theoretical analysis, we reveal that the V-shape dTMDs can significantly increase protein-lipid mismatch, thereby raising the energy barrier of the fusion, and that increasing the number of SNAREs can reduce the energy barrier or protein-lipid mis-match. This study provides a physicochemical mechanistic understanding of SNARE-regulated mem-brane fusion.& COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

In this study, it was demonstrated that the V-shape double transmembrane domains (dTMDs) of syntaxin 17 significantly reduce fusion rate compared with the single transmembrane domain (sTMD). Theoretical analysis revealed that the V-shape dTMDs can increase protein-lipid mismatch, thereby raising the energy barrier of fusion. Increasing the number of SNAREs can reduce the energy barrier or protein-lipid mismatch. This study provides a physicochemical mechanistic understanding of SNARE-regulated membrane fusion.