Fig. 1.

ClpP structure and function. (a) Schematic diagram illustrating the mechanism of function of the ClpX/A–ClpP complex. ClpX/A unfolds and translocates substrate proteins into the ClpP proteolytic chamber for degradation in an ATP-dependent manner (8). ClpX/A molecules can bind ClpP from the top and bottom simultaneously. (b and c) E. coli ClpP side and top views. The axial pores are lined with the N-terminal residues of ClpP (13, 29) that are invisible in the E. coli x-ray structure (1). (d) Detailed view of the ClpP handle region. Residues of the catalytic triad are circled. The Cδ1 atoms of I149 and I151 are indicated by green and red spheres, respectively. The position of the A153C mutation is highlighted in black. Figures displaying molecular structures were prepared with pymol (www.pymol.org).