Fig. 4: The binary Synaptobrevin-2:Syntaxin-1A complex is stabilised by Complexin-1.

a Synaptobrevin-2 and Syntaxin-1A were mixed in a 1:1 ratio and analysed by native MS. Charge state series corresponding to monomeric Synaptobrevin-2 (blue circle) and Syntaxin-1A (orange circles) were observed. b Addition of Complexin-1 to Synaptobrevin-2 and Syntaxin-1A results in formation of the 1:3:1 Synaptobrevin-2:Syntaxin-1A:Complexin-1 complex. Charge state series of monomeric Synatobrevin-2 (blue circles), Syntaxin-1A (orange circles) and Complexin-1 (pink circles), dimeric Syntaxin-1A (orange twin-circles) as well as the 1:3:1 complex (orange-blue-pink circles) are assigned. c The 22+ charge state of the 1:3:1 complex (highlighted in grey in panel b was selected for collision induced dissociation. Dissociated peripheral subunits (Synaptobrevin-2, blue circles; Complexin-1, pink circles) as well as two stripped complexes (3:1 Syntaxin-1A:Complexin-1, orange-pink circles; 3:1 Syntaxin-1A:Synaptobrevin-2, orange-blue circles) are assigned. d Complex formation upon equimolar addition of SNAP25 to the pre-assembled 1:3:1 Synaptobrevin-2:Syntaxin-1A:Complexin-1 complex was followed by native MS. Monomeric Synaptobrevin-2 (blue circles), SNAP25 (green circles) and Complexin-1 (pink circles) as well as the observed complexes (grey triangle-pink circle; blue-yellow-pink circles) are assigned. The observed molecular weight is given for all proteins and complexes (see legend).