SrfJ, a Salmonella type III secretion system effector regulated by PhoP, RcsB, and IolR.
Virulence-related type III secretion systems are present in many Gram-negative bacterial pathogens. These complex devices translocate proteins, called effectors, from the bacterium into the eukaryotic host cell. Here, we identify the product of srfJ, a Salmonella enterica serovar Typhimurium gene regulated by SsrB, as a new substrate of the type III secretion system encoded by Salmonella pathogenicity island 2. The N-terminal 20-amino-acid segment of SrfJ was recognized as a functional secretion and translocation signal specific for this system. Transcription of srfJ was positively regulated by the PhoP/PhoQ system in an SsrB-dependent manner and was negatively regulated by the Rcs system in an SsrB-independent manner. A screen for regulators of an srfJ-lacZ transcriptional fusion using the T-POP transposon identified IolR, the regulator of genes involved in myo-inositol utilization, as an srfJ repressor. Our results suggest that SrfJ is synthesized both inside the host, in response to intracellular conditions, and outside the host, in myo-inositol-rich environments.
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain.
Mar
M
Cordero-Alba
Joaquín
J
Bernal-Bayard
Francisco
F
Ramos-Morales
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D008565:Membrane Proteins; D008840:Microfilament Proteins; C440638:SPI-2 protein, Salmonella; D014157:Transcription Factors; D037521:Virulence Factors; C061064:PhoP protein, Bacteria; C074889:RcsB protein, Bacteria; D001616:beta-Galactosidase