Regulation of the type I protein secretion system by the MisR/MisS two-component system in Neisseria meningitidis

Microbiology (Reading). 2009 May;155(Pt 5):1588-1601. doi: 10.1099/mic.0.023945-0. Epub 2009 Apr 16.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Hemolysin Proteins / genetics
  • Hemolysin Proteins / metabolism*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Molecular Sequence Data
  • Neisseria meningitidis / genetics
  • Neisseria meningitidis / metabolism*
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Transport

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • Hemolysin Proteins
  • Hlyb protein, Bacteria
  • Membrane Transport Proteins