The structure of ClpP at 2.3 angstrom resolution suggests a model for ATP-dependent proteolysis

We have determined the crystal structure of the proteolytic component of the caseinolytic Clp protease (ClpP) from E. coli at 2.3 Angstrom resolution using an ab initio phasing procedure that exploits the internal 14-fold symmetry of the oligomer. The structure of a ClpP monomer has a distinct fold that defines a fifth structural family of serine proteases but a conserved catalytic apparatus. The active protease resembles a hollow, solid-walled cylinder composed of two 7-fold symmetric rings stacked back-to-back. Its 14 proteolytic active sites are located within a central, roughly spherical chamber similar to 51 Angstrom in diameter. Access to the proteolytic chamber is controlled by two axial pores, each having a minimum diameter of similar to 10 Angstrom. From the structural features of ClpP, we suggest a model for its action in degrading proteins.