Chemistry Reference
In-Depth Information
Fig. 3.11
Fluorescence quenching of calcein is used to assay content mixing to confirm liposome
fusion triggered by
Ca
2
+
-synaptotagmin-1
Fig. 3.12
In the absence of
Ca
2
+
, synaptotagmin-1 leads to liposome clustering. This clustering
is mediated by the electrostating binding of synaptotagmin-1 to anionic lipids in the liposomes
fore it can be imagined that the synaptotagmin-1 tethers the liposomes together and
yet keeps them sufficiently far for SNARE nucleation to occur. We estimated how
far synaptotagmin-1 could tether two membranes in various conformations with
coarse-grain molecular dynamics simulations. The C2AB-domain was simulated
based on the available crystal structure (PDB 1DQV). Each individual C2-domain
was conformationally fixed, but had full translational and rotational mobility and
was connected by a flexible linker (residues 266-273), as supported by NMR data.
We then pulled pair-wise on the
Ca
2
+
-binding patches, the polybasic patch and
the N-terminus (Fig.
3.13
). The distances between those sites reflect the maximum
