Fig. 4: Structure of the sialic acid-bound HCE–SV2Ac complex and comparison of the glycan-binding modes between BoNT/E and BoNT/A.
From: Structural basis for botulinum neurotoxin E recognition of synaptic vesicle protein 2
a Cartoon representation of the sialic acid (SIA)-bound HCE–SV2Ac complex with HCE colored in lemon, SV2Ac in orange, and sialic acid in red. An omit electron density map for sialic acid contoured at 1.5σ was overlaid with the final refined model. b A close-up view of the interactions between HCE and sialic acid. One water molecule (W) that mediates the HCE–SIA binding is shown as a cyan sphere. c The HCE–SV2Ac–SIA complex and the HCA–SV2C complex (PDB: 5JLV) were superimposed based on HCE (lemon) and HCA (blue-white). The SIA (red), NAG (orange), and SV2C glycan (blue) are shown as sticks. The SIA-binding and the SV2C-glycan-binding pockets are highlighted in red and blue boxes, respectively. d A close-up view into the SV2C-glycan-binding pocket reveals the differences between HCA (blue-white) and HCE (lemon) in this area. HCE residue Q1250 would clash with the SV2C glycan based on the superposition. e A close-up view into the SIA-binding pocket shows that this pocket is partly conserved between HCE and HCA.
