A family of bacterial cysteine protease type III effectors utilizes acylation-dependent and -independent strategies to localize to plasma membranes

J Biol Chem. 2009 Jun 5;284(23):15867-79. doi: 10.1074/jbc.M900519200. Epub 2009 Apr 3.


Bacterial phytopathogens employ a type III secretion system to deliver effector proteins into the plant cell to suppress defense pathways; however, the molecular mechanisms and subcellular localization strategies that drive effector function largely remain a mystery. Here, we demonstrate that the plant plasma membrane is the primary site for subcellular localization of the Pseudomonas syringae effector AvrPphB and five additional cysteine protease family members. AvrPphB and two AvrPphB-like effectors, ORF4 and NopT, autoproteolytically process following delivery into the plant cell to expose embedded sites for fatty acylation. Host-dependent lipidation of these three effectors directs plasma membrane localization and is required for the avirulence activity of AvrPphB. Surprisingly, the AvrPphB-like effectors RipT, HopC1, and HopN1 utilize an acylation-independent mechanism to localize to the cellular plasma membrane. Although some AvrPphB-like effectors employ acylation-independent localization strategies, others hijack the eukaryotic lipidation machinery to ensure plasma membrane localization, illustrating the diverse tactics employed by type III effectors to target specific subcellular compartments.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acylation
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cell Membrane / enzymology*
  • Cloning, Molecular
  • Cosmids
  • Cysteine Endopeptidases / chemistry
  • Cysteine Endopeptidases / genetics*
  • Cysteine Endopeptidases / metabolism*
  • Genetic Vectors
  • Molecular Sequence Data
  • Open Reading Frames
  • Polymerase Chain Reaction
  • Protein Biosynthesis
  • Pseudomonas syringae / enzymology*
  • Rhizobium / enzymology
  • Rhodopseudomonas / enzymology
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription, Genetic


  • Bacterial Proteins
  • Cysteine Endopeptidases