Extended Data Figure 8. Structure comparison of the Syt1-SNARE-Cpx-Syt1 crystal structures and other known crystal structures.

a–c, Conserved and variable regions of the SNARE-Cpx subcomplex in the Syt1-SNARE-Cpx-Syt1 C2B crystal structure (colored), and crystal structures of the SNARE-Cpx subcomplex (PDB code 1KIL²⁹, black and PDB code 3RK3³⁴, white). The interaction between the central a-helix of Cpx and the SNARE complex is essentially identical in all crystal structures, while the angle at which the accessory helix protrudes away from the SNARE complex is variable. Such variability was also observed by single molecule fluorescence resonance transfer experiments⁴¹. d, The superposition of the Syt1 C2B domain of the Syt1-SNARE-Cpx-Syt1 C2AB crystal structure with crystal structures of uncomplexed C2AB fragments (PDB codes are indicated in the figure) illustrates variability of the position of the C2A domain relative to the C2B domain of Syt1.