Extended Data Figure 7. DNA end binding by α1 bridges active site conformations to DNA end sensing status.

a, Structural overlays of three states reported in this study. b. Conformational rearrangements localize to the HIT N-terminal helix and the HIT HΦHΦH loop. HIT-α1 is found in variable conformations, and movement of α1 is linked to rearrangement of the active site HΦHΦH loop. The conformation of Met 256, His260 and His258 is modulated by van der Waals interactions with Leu171 and Trp167 from α1 that together flank the HΦHΦH loop. In the disassembled active site conformer of the product complex, α1 migrates ~4 Å away from HΦHΦH, with concomitant morphing of His260 conformation into an inactive state. c, Transition state complex σ-A weighted 2.55 Å 2Fo-Fc electron density map is displayed contoured at 1.0 σ for the active site. A yellow sphere, “V”, marks the position of the vanadium covalently bonded to His260, the 5′-phosphate of 5′-rG and adenosine. d, Product complex (assembled active site) σ-A weighted 1.95 Å 2Fo-Fc electron density map is displayed contoured at 1.5 σ for the active site. e, Product complex (disassembled active site) σ-A weighted 1.95 Å 2Fo-Fc electron density map is displayed contoured at 1.5 σ.