?-SNAP Enhances SNARE Zippering by Stabilizing the SNARE Four-Helix Bundle.

ABSTRACT: Intracellular membrane fusion is mediated by dynamic assembly and disassembly of soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors (SNAREs). ?-SNAP guides NSF to disassemble SNARE complexes after membrane fusion. Recent experiments showed that ?-SNAP also dramatically enhances SNARE assembly and membrane fusion. How ?-SNAP is involved in these opposing activities is not known. Here, we examine the effect of ?-SNAP on the stepwise assembly of the synaptic SNARE complex using optical tweezers. We found that ?-SNAP destabilized the linker domain (LD) of the SNARE complex but stabilized its C-terminal domain (CTD) through a conformational selection mechanism. In contrast, ?-SNAP minimally affected assembly of the SNARE N-terminal domain (NTD), indicating that ?-SNAP barely bound the partially assembled trans-SNARE complex. Thus, ?-SNAP recognizes the folded CTD for SNARE disassembly with NSF and subtly modulates membrane fusion by altering the stabilities of the SNARE CTD and LD.

SUBMITTER: Ma L 

PROVIDER: S-EPMC4838522 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature