The Harpin-PSS (HrpZ; TC# 1.C.56.1.1) protein is secreted by Pseudomonas syringae via the Hrp secretion system (IIISP; TC# 3.A.6) and elicits a hypersensitive response (HR) in non-host plants upon infection and pathogenicity in hosts.
HrpZ - a harpin - is a highly thermostable protein that exhibits multifunctional abilities, e.g., it elicits the hypersensitive response (HR), enhances plant growth, acts as a virulence factor, and forms pores in plant plasma membranes as well as artificial membranes.
[3][4] When inserted into liposomes and synthetic bilayers at low concentrations (2 nM), it provokes a cation-selective ion current with large unitary conductance.
It has been hypothesized that such channels could allow nutrient release and/or delivery of virulence factors during bacterial colonization of host plants.
[3] The generalized transport reaction thought to be catalyzed by HrpZ is:[4]