title: Harpin of Pseudomonas syringae pv. phaseolicola harbors a protein binding site.
abstract: Harpin HrpZ of plant-pathogenic bacterium Pseudomonas syringae elicits a hypersensitive response (HR) in some nonhost plants, but its function in the pathogenesis process is still obscure. HrpZ-interacting proteins were identified by screening a phage-display library of random peptides. HrpZ of the bean pathogen P. syringae pv. phaseolicola (HrpZPph) shows affinity to peptides with a consensus amino acid motif W(L)ARWLL(G/L). To localize the peptide-binding site, the hrpZPph gene was mutagenized with randomly placed 15-bp insertions, and the mutant proteins were screened for the peptide-binding ability. Mutations that inhibited peptide-binding localized to the central region of hrpZPph, which is separate from the previously determined HR-inducing region. Antiserum raised against one of the hrpZPph-binding peptides recognized small proteins in bean, tomato, parsley, and Arabidopsis thaliana but none in tobacco. On native protein blots, hrpZPph bound to a bean protein with similar pI as the protein recognized by the peptide antiserum. The result suggests a protein-protein interaction between the harpin and a host plant protein, possibly involved in the bacterial pathogenesis.
authors.affiliation: General Microbiology, Department of Biological and Environmental Sciences, FI-00014 University of Helsinki, Finland.
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Li
authors.forename: Minna
authors.initials: M
authors.lastname: Haapalainen
authors.forename: Justin
authors.initials: J
authors.lastname: Lee
authors.forename: Thorsten
authors.initials: T
authors.lastname: Nürnberger
authors.forename: Martin
authors.initials: M
authors.lastname: Romantschuk
authors.forename: Suvi
authors.initials: S
authors.lastname: Taira
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D001665:Binding Sites; D008969:Molecular Sequence Data; D019151:Peptide Library; D010940:Plant Proteins / Q000378:metabolism; D011485:Protein Binding; D044224:Pseudomonas syringae / Q000737:chemistry*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D019151:Peptide Library; D010940:Plant Proteins; C087295:HrpZ protein, Pseudomonas syringae