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. Author manuscript; available in PMC: 2026 May 30.
Published before final editing as: Cell Rep. 2026 Apr 10;45(4):117231. doi: 10.1016/j.celrep.2026.117231

Figure 3. Comparison of the crosslinked HflK/CSS closed conformation with the open structure.

Figure 3.

(A) The sliced top and side view representations of the DDM-solubilized HflK/CSS complex map obtained from heterogeneous refinement Figure S4), showing one FtsH residing inside the closed HflK/C assembly.

(B) Overlay of the hat region from the crosslinked HflK/CSS (yellow) and the open, nautilus-like structure (PDB: 9CZ2, green), shown in top and side views.

(C) Top-view overlay of the full HflK/CSS and the open, nautilus-like structure (PDB: 9CZ2) reveals that the overall arrangement is largely conserved; conformational differences are localized to the HflK and HflC subunits at the opening of the nautilus-like conformation (root-mean-square deviation [RMSD] = 1.7 Å).

(D) Sliced top view of (C), highlighting that the positions of FtsH subunits (pink) from the nautilus-like conformation (PDB: 9CZ2) do not cause any steric clashes with the closed HflK/CSS conformation. Arrows indicate the direction of the movement of the HflK and HflC subunits from the open to the closed structure.