title: NopB, a type III secreted protein of Rhizobium sp. strain NGR234, is associated with pilus-like surface appendages.
abstract: Rhizobium sp. strain NGR234 possesses a functional type three secretion system (TTSS), through which a number of proteins, called nodulation outer proteins (Nops), are delivered to the outside of the cell. A major constraint to the identification of Nops is their low abundance in the supernatants of NGR234 strains grown in culture. To overcome this limitation, a more sensitive proteomics-based strategy was developed. Secreted proteins from wild-type NGR234 were separated by two-dimensional gel electrophoresis, and the gel was compared to similar gels containing the proteins from a TTSS mutant (NGROmegarhcN). To identify the proteins, spots unique to the NGR234 gels were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and the data were compared to the sequence of the symbiotic plasmid of NGR234. A nonpolar mutant of one of these proteins was generated called NopB. NopB is required for Nop secretion but inhibits the interaction with Pachyrhizus tuberosus and augments nodulation of Tephrosia vogelii. Flavonoids and a functional TTSS are required for the formation of some surface appendages on NGR234. In situ immunogold labeling and isolation of these pili showed that they contain NopB.
authors.affiliation: LBMPS, Département de Biologie Végétale, Université de Genève, Sciences III, Geneva, Switzerland.
authors.forename: Maged M
authors.initials: MM
authors.lastname: Saad
authors.forename: Hajime
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Corinne
authors.initials: C
authors.lastname: Marie
authors.forename: Ian R
authors.initials: IR
authors.lastname: Brown
authors.forename: John W
authors.initials: JW
authors.lastname: Mansfield
authors.forename: William J
authors.initials: WJ
authors.lastname: Broughton
authors.forename: William J
authors.initials: WJ
authors.lastname: Deakin
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D016384:Consensus Sequence; D030562:Databases, Protein; D010861:Fimbriae, Bacterial / Q000648:ultrastructure*; D008969:Molecular Sequence Data; D010957:Plasmids; D012231:Rhizobium / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins