Fig. 3: Apo hClpP undergoes key conformational changes upon binding to hClpX.

a 3D reconstruction and b atomic model of C1 refined apo hClpP. The N-terminal loops of three hClpP subunits form well-ordered β-hairpins and are pointed upwards, while the N-terminal loops of the remaining subunits are disordered. The inset highlighted with a magenta box shows one of the three well-ordered N-terminal β-hairpins c Overlay of the apo hClpP (shown in burlywood) and the top part of the hClpX-bound hClpP tetradecamer (shown in grey). The insets highlight conformational changes in three different regions of hClpP upon binding to hClpX: (1) inward movement of the handle region; (2) a downward movement of the C-terminal extension; (3) outward movement of the N-terminal loops from the central pore as well as the ordering of the N-terminal loops in the subunits that originally had disordered loops.