Fig. 4. Rearrangement of ClpX-ClpP contacts correlates with upward movement of the seam subunit.

In many ClpXP complexes, the empty binding cleft on a ClpP₇ ring lies between the clefts occupied by the IGF loops of ClpX subunits E⁵ and F^seam (A; PDB code 6WRF). In the structures presented here and some other ClpXP structures (B; PDB code 8V9R), the IGF loop of chain E⁵ moves into a binding cleft that is unoccupied in structures similar to that in (A). These movements correlate with F^seam upward movement, as shown in (C, D).