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Journal of Bacteriology, February 1999, p. 1126-1133, Vol. 181, No. 4
St. Jude Children's Research Hospital,
Memphis, Tennessee 381051;
Division of
Infectious Diseases, Department of Research, University Hospital,
CH-4031 Basel, Switzerland2; and
Department of Cell Biology, New York University Medical
Center, New York, New York 100163
Received 3 September 1998/Accepted 5 December 1998
The Escherichia coli Pst system belongs to the family
of ABC transporters. It is part of a phosphate (PHO) regulon which is regulated by extracellular phosphate. Under conditions of phosphate limitation, the response regulator PhoB is phosphorylated by the histidine kinase PhoR and binds to promoters that share a consensus PHO
box. Under conditions of phosphate excess, PhoR, Pst, and PhoU
downregulate the PHO regulon. Screening of a library of pneumococcal mutants with defects in exported proteins revealed a putative two-component regulatory system, PnpR-PnpS, and a downstream ABC transporter, similar to the Pst system in E. coli including
a gene encoding a PhoU protein. Similar to E. coli,
mutagenesis of the ATP-binding cassette gene, pstB,
resulted in decreased uptake of phosphate. The effects of the loss of
the pneumococcal Pst system extended to decreased transformation and
lysis. Withdrawal of phosphate led to transformation deficiency in the
parent strain R6x but not to penicillin tolerance, suggesting that
reduced bacterial death was independent of phosphate. None of these
phenotypes was observed in the pneumococcal loss-of-function mutant
phoU. By using a lacZ reporter construct, it
was demonstrated that expression of the two-component regulatory system
PnpR-PnpS was not influenced by different concentrations of phosphate.
These results suggest a more complex role of the Pst system in
pneumococcal physiology than in that of E. coli.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Identification of a Streptococcus
pneumoniae Gene Locus Encoding Proteins of an ABC Phosphate
Transporter and a Two-Component Regulatory System
*
Corresponding author. Mailing address: Dept. of
Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105. Phone: (901) 495-3486. Fax: (901)
495-3099. E-mail: elaine.tuomanen{at}stjude.org.
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