Supplementary Figure 1: Effects of Syt1 C₂AB on the ¹H-¹⁵N HSQC spectra of the SNARE complex.

(a) Diagram depicting the proteins involved in neurotransmitter release discussed in this study. The SNARE complex is depicted as a four-helix bundle with Synaptobrevin in red, Syntaxin-1 in yellow and SNAP-25 in green and blue. The N-terminal region of Syntaxin-1 is not shown for simplicity. The SNARE complex is shown partially formed and full zippering of the Synaptobrevin SNARE motif to complete the four-helix bundle is believed to be key for membrane fusion. Syt1 is shown in orange with the C₂A and C₂B domains labeled as A and B, respectively, while CpxI is shown in gray (central helix) and pink (accessory helix). The location of CpxI is based on the crystal structure of the CpxI(26-83)-SNARE complex¹. The position of Syt1 is arbitrary and is the subject of this study. Only one molecule each of Syt1 and of CpxI are shown for simplicity but each SNARE complex is expected to have one molecule of Syt1 and one of CpxI bound. (b-d) ¹H-¹⁵N TROSY HSQC spectra of 40 μM SNARE complex samples ²H,¹⁵N-labeled at the syntaxin-1 (b), synaptobrevin (c), SNAP-25 N-terminal (SNN) (d) and SNAP-25 C-terminal (SNC) (e) SNARE motifs in the absence (black contours) and presence (red contours) of 20 μM C₂AB.