HrpZ Family
The Pseudomonas syringae HrpZ Cation Channel Family is a member of the RTX-toxin superfamily. The Harpin-PSS protein is secreted by Pseudomonas syringae via the Hrp secretion system and elicits a hypersensitive response in non-host plants upon infection and pathogenicity in hosts. It contains several repetitive regions and exhibits two extended regions of moderate hydrophobicity that might serve as α-helical TMSs. The HrpZ cation channel is predicted to be largely of α-structure. HrpZ - a harpin - is a highly thermostable protein that exhibits multifunctional abilities, e.g., it elicits the hypersensitive response, enhances plant growth, acts as a virulence factor, and forms pores in plant plasma membranes as well as artificial membranes. Homologues are not found in organisms other than P. syringae.