FIG. 7.

Schematic model of the autocleavage of HtrA. HtrA reorganizes into large cages that encapsulate the substrate for degradation. Once full-length substrate has been degraded, the HtrA reverts to its hexameric resting state, and peptides generated during substrate hydrolysis allosterically activate HtrA, inducing the self-cleavage process. PDB files 1ky9 and 2zle for the hexameric and 12-mer HtrA cages, respectively, were obtained from the Protein Data Bank and are displayed with the program UCSF Chimera (http://www.cgl.ucsf.edu/chimera).