Fig. 1: Structural basis of MT3 regulation on target receptors.
a Overall structures of MT3 in complex with α1A (left), α2A (middle) and M4AChR (right). MT3 is shown in orange, α1A in purple, α2A in blue, and M4AChR in green. This color scheme is consistently used throughout all subsequent figures unless otherwise noted. b Comparison of the receptor engagement modes between MT3 and MT7. The structures of MT3-M4AChR and MT7-M1AChR (PDB ID: 6WJC) were aligned based on the receptor component. MT7 and M1AChR are shown in blue and cyan, respectively. For clarity, only Finger1 and Finger2 of the toxins are shown in the top view. c Occupation of the orthostatic site by the MT3 residue R34 (orange sphere). The orthostatic ligands (shown as sticks) were modeled according to structures with the PDB IDs of 7YMJ (for α1A, left), 6KUX (for α2A, middle) and 5DSG (for M4AChR, right). d Conformational differences between MT3-stabilized receptors and those bound to chemical ligands. Structures of α1A with tamsulosin (green), α2A with RSC (yellow), and M4AChR with tiotropium (purple) are compared to their corresponding MT3-stabilized forms. Major conformational changes are highlighted with red arrows.
