Figure 2. An EF-X experiment in the LNX2^PDZ2 domain.

a, LNX2^PDZ2 binds target ligands (in yellow) in a groove between the β₂ and α₂ segments. The binding site is coupled to allosteric sites on the β₂–β₃ segment and the α₁–β₄ segment (through the β₁–β₂ loop and α₁ helix). b, Data collection involves four sequential X-ray exposures for each crystal orientation: no voltage (OFF), and three time delays (50, 100, 200 ns) after onset of the voltage pulse. One second is allowed between pulses for crystal cooling. HV, high voltage. c, The protocol in b is repeated for a series of crystal rotations to collect a full diffraction data set. d, LNX2^PDZ2 crystallizes in the C2 space group, which includes two kinds of rotational symmetry (black symbols); this results in four molecules per unit cell and one molecule per asymmetric unit. e, With the electric field E (applied along the a dimension), all rotational symmetry is broken. This results in a new unit cell with two molecules per asymmetric unit (red and blue)—one experiencing + E, and one experiencing − E.