Figure 4.

Integrin α4β7 headpiece structures from the MD simulation. (A) The initial structure of integrin α4β7 headpiece for MD simulation. (B–D) Snapshots of integrin α4β7 headpiece structures in closed, low-affinity state (B), intermediate state with a distance of 5.2 nm between the Thigh and PSI domains (C), and intermediate state with a distance of 7.8 nm between the Thigh and PSI domains (D). MIDAS was occupied by Mg²⁺, and ADMIDAS and SyMBS were occupied by Ca²⁺. (E) Snapshot of integrin α4β7 headpiece structure in fully open active state with a distance of 9.35 nm between the Thigh and PSI domains. MIDAS, ADMIDAS, and SyMBS were occupied by Mn²⁺. The three metal ion binding sites are SyMBS, MIDAS, and ADMIDAS from left to right.