Regulation of the type I protein secretion system by the MisR/MisS two-component system in Neisseria meningitidis.
Neisseria meningitidis, an obligate human pathogen, remains a leading cause of meningitis and fatal sepsis. Meningococci are known to secrete a family of proteins, such as FrpC, with sequence similarity to the repeat-in-toxin (RTX) proteins via the type I secretion system. The meningococcal type I secretion proteins are encoded at two distant genetic loci, NMB1400 (hlyB) and NMB1738/1737 (hlyD/tolC), and are separated from the RTX toxin-like substrates. We have characterized the promoter elements of both hlyB and hlyD by primer extension and lacZ reporter fusions and revealed the growth phase-dependent upregulation of both genes. In addition, we showed that the MisR/MisS two-component system negatively regulates the expression of hlyB and hlyD/tolC. Direct binding of MisR to hlyB and hlyD promoters was demonstrated by electrophoretic mobility shift assay (EMSA), and DNase I protection assays identified MisR binding sites overlapping the promoter elements. Direct repression of hlyB transcription by MisR was supported by in vitro transcription assays. Mutations in the MisR/S system affected, but did not eliminate, the growth phase-dependent upregulation of hlyB, suggesting additional regulatory mechanisms. Increased secretion of RTX toxin-like proteins was detected in the cell-free media from misS mutant cultures, indicating that the amounts of extracellular RTX toxin-like proteins are, in part, controlled by the abundance of the type I secretion apparatus. This is, to our knowledge, the first example of a two-component system mediating secretion of cytotoxin family proteins by controlling expression of the type I secretion proteins.
Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
Soma
S
Sannigrahi
Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
Xinjian
X
Zhang
Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
Yih-Ling
YL
Tzeng
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D021381:Protein Transport
D001426:Bacterial Proteins; D002352:Carrier Proteins; D006460:Hemolysin Proteins; C050837:Hlyb protein, Bacteria; D026901:Membrane Transport Proteins