HrpZ Family

The Pseudomonas syringae HrpZ Target Host Cell Membrane Cation Channel (HrpZ) Family (TC# 1.C.56) is a member of the RTX-toxin superfamily. 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. It contains several repetitive regions and exhibits two extended (20 residue) regions of moderate hydrophobicity that might serve as α-helical TMSs. They are predicted to be largely of α-structure. Homologues are not found in organisms other than P. syringae.[1][2]

Function

HrpZ when inserted into liposomes and synthetic bilayers at low concentrations (2 nM) provokes a cation-selective ion current with large unitary conductance. Chloride is not transported. It has been hypothesized that such channels could allow nutrient release and/or delivery of virulence factors during bacterial colonization of host plants.[1]

Transport Reaction

The generalized transport reaction thought to be catalyzed by HrpZ is:[2]

Small molecules (in) → Small molecules (out)

References

  1. 1 2 Lee, J.; Klusener, B.; Tsiamis, G.; Stevens, C.; Neyt, C.; Tampakaki, A. P.; Panopoulos, N. J.; Nöller, J.; Weiler, E. W. (2001-01-02). "HrpZ(Psph) from the plant pathogen Pseudomonas syringae pv. phaseolicola binds to lipid bilayers and forms an ion-conducting pore in vitro". Proceedings of the National Academy of Sciences of the United States of America 98 (1): 289–294. doi:10.1073/pnas.011265298. ISSN 0027-8424. PMC 14583. PMID 11134504.
  2. 1 2 Saier, MH Jr. "1.C.56 The Pseudomonas syringae HrpZ Target Host Cell Membrane Cation Channel (HrpZ) Family". Transporter Classification Database. Saier Lab Bioinformatics Group / SDSC.

Further Reading

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