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Author Notes:

Correspondence: Yih-Ling Tzeng: ytzeng@emory.edu

Present address: Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.

We thank Shaojia Bao for technical assistance.

Subjects:

Research Funding:

This work was supported by grant AI061031 to Y.-L. T. from the National Institutes of Health.

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

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Journal Title:

Microbiology

Volume:

Volume 155, Number Pt 5

Publisher:

, Pages 1588-1601

Type of Work:

Article | Post-print: After Peer Review

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.

Copyright information:

© 2009, SGM

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