title: Flagellar proteins and type III-exported virulence factors are the predominant proteins secreted into the culture media of Salmonella typhimurium.
abstract: We analysed all major proteins secreted into culture media from Salmonella typhimurium. Proteins in culture supernatants were collected by trichloroacetic acid precipitation, separated in SDS-polyacrylamide gels and analysed by amino acid sequencing. Wild-type strain SJW1103 cells typically gave rise to nine bands in SDS gels: 89, 67, 58, 52, 50, 42, 40, 35 and (sometimes) 28 kDa. A search of the sequences in the available databases revealed that they were either flagellar proteins or virulence factors. Six of them were flagella specific: FlgK or HAP1 (58 kDa), FliC or flagellin (52 kDa), FliD or HAP2 (50 kDa), FlgE or hook protein (42 kDa), FlgL or HAP3 (35 kDa) and FlgD or hook-cap protein (28 kDa). The other four bands were specific for virulence factors: SipA (89 kDa), SipB (67 kDa), SipC (42 kDa) and InvJ (40 kDa). The 42 kDa band was a mixture of FlgE and SipC. We also analysed secreted proteins from more than 30 flagellar mutants, and they were categorized into four groups according to their band patterns: wild type, mot type, polyhook type and master gene type. Virulence factors were constantly secreted at a higher level in all flagellar mutants except a deltamot (motAB deletion) mutant, in which the amounts were greatly reduced. A new morphological pathway of flagellar biogenesis including protein secretion is presented.
authors.affiliation: Department of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya 320-8551, Japan. Department of Applied Biochemistry, Utsunomiya University, Utsunomiya 321-8505, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Komoriya
authors.forename: N
authors.initials: N
authors.lastname: Shibano
authors.forename: T
authors.initials: T
authors.lastname: Higano
authors.forename: N
authors.initials: N
authors.lastname: Azuma
authors.forename: S
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: S I
authors.initials: SI
authors.lastname: Aizawa
mesh_terms: D000199:Actins / Q000737:chemistry / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D005407:Flagella / Q000378:metabolism* / Q000502:physiology; D005408:Flagellin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification; D008840:Microfilament Proteins; D009154:Mutation; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D017421:Sequence Analysis; D014774:Virulence
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D003470:Culture Media; C088720:FlgD protein, Salmonella typhimurium; C097681:FlgE protein, Bacteria; C088595:FlgK protein, Bacteria; D008565:Membrane Proteins; D008840:Microfilament Proteins; C094578:Salmonella invasion protein C; C118287:SipA protein, Salmonella; C094579:invasion protein B, Salmonella typhimurium; D005408:Flagellin