Molecular Playground/Pcr H

PcrH

Many Gram-negative pathogens use a Type III secretion (T3S) system to inject effector proteins into the cytoplasm of their target cell. These effectors need to translocate through the plasma membrane, presumably through a proteinaceous structure, the translocon. Substantial genetic and biochemical data indicate the translocon is composed by two T3S proteins, in the case of Pseudomonas aeruginosa, the translocators PopB and PopD. Since PopB and PopD can bind to lipid bilayers and form pores in them, they need to be maintained in a state competent for secretion and also not toxic for the bacterial cell. PrcH is a bacterial co-chaperone responsible for this (Dimer structure shown in Blue/Green). PcrH binds to a present in both PopB and PopD (9 residue peptide (Pink) shown bound to Chain A in structure (Blue)) and keeps them in a metastable non oligomeric state. It is also believed that PcrH has an active role in delivering PopB and PopD to the basal body of the T3S system, where an ATPse unfolds and secretes the translocators PopB and PopD. PcrH's characteristic fold is composed of Tetratricopeptide Repeats (TPR repeats). This fold is also present in Eukaryotic co-chaperons such as HOP. Given its key role in molecular pathogenesis PcrH is a potential target for drug design.