RT Journal Article
SR Electronic
T1 Exploring the conformational changes of the Munc18-1/syntaxin 1a complex
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2022.11.29.518383
DO 10.1101/2022.11.29.518383
A1 Ioanna Stefani
A1 Justyna Iwaszkiewicz
A1 Dirk Fasshauer
YR 2022
UL http://biorxiv.org/content/early/2022/11/29/2022.11.29.518383.abstract
AB Neurotransmitters are released from synaptic vesicles, the membrane of which fuses with the plasma membrane upon calcium influx. This membrane fusion reaction is driven by the formation of a tight complex comprising the plasma membrane SNARE proteins syntaxin-1a and SNAP-25 with the vesicle SNARE protein synaptobrevin. The neuronal protein Munc18-1 forms a stable complex with syntaxin-1a. Biochemically, syntaxin-1a cannot escape the tight grip of Munc18-1, so formation of the SNARE complex is inhibited. However, Munc18-1 is essential for the release of neurotransmitters in vivo. It has therefore been assumed that Munc18-1 makes the bound syntaxin-1a available for SNARE complex formation. Exactly how this occurs is still unclear, but it is assumed that structural rearrangements occur. Here, we used a series of mutations to specifically weaken the complex at different critical positions in order to induce these rearrangements biochemically. Our approach was guided through sequence and structural analysis and supported by molecular dynamics simulations. Subsequently, we created a homology model showing the complex in an altered conformation. This conformation presumably represents a more open arrangement of syntaxin-1a that permits the formation of SNARE complex to be initiated while still bound to Munc18-1. In the future, research should investigate how this central reaction for neuronal communication is controlled by other proteins.Competing Interest StatementThe authors have declared no competing interest.(SNAREs)N-ethylmaleimide-sensitive factor attachment receptors(CATCHR)complex associated with tethering containing helical rods(SAXS)Small-angle X-ray scattering(SM)Sec1/Munc18(MD)molecular dynamics