title: The Predicted Lytic Transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria Associates with the Type III Secretion System and Promotes Effector Protein Translocation.
abstract: The pathogenicity of the Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which spans both bacterial membranes and translocates effector proteins into plant cells. The assembly of the T3S system presumably involves the predicted lytic transglycosylase (LT) HpaH, which is encoded adjacent to the T3S gene cluster. Bacterial LTs degrade peptidoglycan and often promote the formation of membrane-spanning macromolecular protein complexes. In the present study, we show that HpaH localizes to the bacterial periplasm and binds to peptidoglycan as well as to components of the T3S system, including the predicted periplasmic inner rod proteins HrpB1 and HrpB2 as well as the pilus protein HrpE. In vivo translocation assays revealed that HpaH promotes the translocation of various effector proteins and of early substrates of the T3S system, suggesting a general contribution of HpaH to type III-dependent protein export. Mutant studies and the analysis of reporter fusions showed that the N-terminal region of HpaH contributes to protein function and is proteolytically cleaved. The N-terminally truncated HpaH cleavage product is secreted into the extracellular milieu by a yet-unknown transport pathway, which is independent of the T3S system.
authors.affiliation: Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hausner
authors.affiliation: Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Hartmann
authors.affiliation: Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Jordan
authors.affiliation: Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany daniela.buettner@genetik.uni-halle.de.
authors.forename: Daniela
authors.initials: D
authors.lastname: Büttner
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018387:Codon, Initiator; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D008968:Molecular Conformation; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism; D046928:Peptidoglycan Glycosyltransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000382:microbiology; D011485:Protein Binding; D014176:Protein Biosynthesis; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D000069296:Type III Secretion Systems; D016959:Xanthomonas campestris / Q000502:physiology*; D044184:Xanthomonas vesicatoria / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D018387:Codon, Initiator; D010457:Peptidoglycan; D011993:Recombinant Fusion Proteins; D000069296:Type III Secretion Systems; D046928:Peptidoglycan Glycosyltransferase
keywords: Slt70; Xanthomonas; effector proteins; lytic transglycosylase; peptidoglycan; type III secretion