Flagellar proteins and type III-exported virulence factors are the predominant proteins secreted into the culture media of Salmonella typhimurium.
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.
Komoriya
K
K
Department of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya 320-8551, Japan. Department of Applied Biochemistry, Utsunomiya University, Utsunomiya 321-8505, Japan.
Shibano
N
N
Higano
T
T
Azuma
N
N
Yamaguchi
S
S
Aizawa
S I
SI
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
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