Structural insights into the molecular mechanisms of myasthenia gravis and their therapeutic implications
- University of Southern California, United States
- Keck School of Medicine, University of Southern California, United States
Figures
Figure 1 with 3 supplements
The ternary complex of nAChR α1 ECD bound by Fab35 and α-Btx.
(a) Gel shift assay. Native PAGE showed the formation of the ternary complex of nAChR α1 ECD, α-Btx and Fab35. Lane 1: nAChR α1 ECD alone (labeled as α1 ECD), Lane 2: α-Btx alone, Lane 3: Fab35 …
Figure 1—figure supplement 1
Key structural features of the human nAChR α1 ECD.
Our study also generated the first atomic picture of the human nAChR α1 ECD, which appears very similar to the previously characterized mouse nAChR α1 ECD (PDB ID, 2QC1) (Lindstrom, 2000). Many …
Figure 1—figure supplement 2
Structural differences between the human and mouse nAChR α1 ECDs.
A significant structural difference between the human and mouse nAChR α1 ECDs is the binding interface of α-Btx. (a) In the mouse nAChR α1 ECD, Phe189 is inserted into a surface pocket of α-Btx. (b) …
Figure 1—figure supplement 3
Structural comparison of mouse nAChR α1 ECDs in the ternary complex of Fab35/nAChR α1 ECD/α-Btx and the binary complex of nAChR α1 ECD/α-Btx.
(a) Superposition of the mouse nAChR α1 ECD from the Fab35/nAChR α1 ECD/α-Btx complex (blue) and the nAChR α1 ECD/α-Btx complex (green) (PDB ID, 2QC1) (Lindstrom, 2000) using the Cα backbone of the …
Figure 2
Mutual insertion of loops into pockets of binding partners.
(a) The MIR loop of nAChR α1 inserts into a surface pocket between the variable domains of the heavy and light chains (VH and VL) of Fab35 (orange) while the N-terminal helix sits into a groove on …
Figure 3 with 1 supplement
Detailed interactions at the interface between Fab35 and nAChR α1 ECD.
(a) Binding interactions at the Asp71 site of α1 (located at the MIR). (b) Binding interactions at the Asn68 site of α1 (located at the MIR). (c) Binding interactions surrounding Arg6 and Lys10 of …
Figure 3—figure supplement 1
Fo-Fc omit maps of the interface between Fab35 and nAChR α1 ECD.
The Fo-Fc omit maps of representative side chains and main chains (only interacting ones) of the Fab35-alpha1 residues and waters at the binding interface. The Fo-Fc omit maps are shown in green and …
Figure 4 with 1 supplement
Structural comparisons among MG mAbs.
(a) Superposition of Fab198 (Poulas et al., 2001) (heavy chain: purple and light chain: dark green) onto Fab35 in the Fab35/nAChR α1/α-Btx ternary complex using the Cα backbone. (b) Detailed …
Figure 4—figure supplement 1
Structural comparison between Fab35 and Fab198/Fab192.
(a) A surface model showing that the CDR-H3 loop of Fab198 (PDB ID, 1FN4) (purple) (Engel and Arahata, 1987) is too short to interact with the surface pocket of nAChR α1, which is, on the other …
Figure 5
Specificity of antibody-receptor binding.
(a) Multiple sequence alignment of the N-terminal α helix (left) and the MIR (right) of human nAChR family members. The sequence of human nAChR α1 (hα1) in the crystal structure is underlined. …
Figure 6 with 1 supplement
Modeling the binding of Fab35 to a nAChR pentamer.
(a) Superposition of the Fab35/nAChR α1 ECD/α-Btx ternary complex on one subunit of the α7/AChBP chimera pentamer (blue) (PDB ID, 3SQ9) (Li et al., 2011) using the Cα backbone of ECDs as the …
Figure 6—figure supplement 1
Modeling the binding of a complete MG mAb to full-length nAChR(s).
(a) Modeling of the binding of a complete antibody (Fab+Fc) to a nAChR pentamer using the Torpedo nAChR as a template. The ternary Fab35/nAChR α1 ECD/α-Btx complex structure was used to guide the …
Additional files
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Supplementary file 1
The statistics of data collection and structure refinement for Fab35/human nAChR α1 ECD/α-Btx ternary complexes and Fab35/mouse nAChR α1 ECD/α-Btx ternary complexes.
- https://doi.org/10.7554/eLife.23043.015
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Supplementary file 2
Contacting residues at the Fab35/human nAChR α1 ECD interface.
Residues at the Fab35/human nAChR α1 (α211) interface were mapped using the contact program in CCP4 with a 4.5 Å distance cutoff (Winn et al., 2011). For each residue of nAChR α1 involved in antibody binding (Chain B/α211 listed in the first column), its interacting residues from the light chain (Chain C listed in the second column) and the heavy chain (Chain D listed in the third column) of Fab35 are listed in the corresponding row. Residues on the N-terminal helix is highlighted in yellow and residues on the MIR loop is highlighted in light green. Note that several nAChR α1 residues, including R6, K10, N68 and D71/Y72 (red font), contact a large number of antibody residues. These residues can be considered as ‘hotspots’ of the binding interface. Y72 can be considered as part of the Asp71 ‘hotspot’ (see the text).
- https://doi.org/10.7554/eLife.23043.016
