The pst operon of Bacillus subtilis has a phosphate-regulated promoter and is involved in phosphate transport but not in regulation of the pho regulon

Abstract

Genes from Bacillus subtilis predicted to encode a phosphate-specific transport (Pst) system were shown by mutation to affect high-affinity P i uptake but not arsenate resistance or phosphate (Pho) regulation. The transcription start of the promoter upstream of the pstS gene was defined by primer extension. The promoter contains structural features analogous to the Escherichia coli pst promoter but not sequence similarity. Expression from this promoter was induced >5,000-fold upon phosphate starvation and regulated by the PhoP-PhoR two-component regulatory system. These data indicate that the pst operon is involved in phosphate transport and is a member of the Pho regulon but is not involved in P i regulation.Escherichia coli has two major P i transport systems (24,29,30,35,44). The Pst (phosphate-specific transport) system is a high-affinity, low-velocity, free-P i transport system which is structurally similar to ABC transporters (3). The Pit (phosphate inorganic transport) system is a divalent metal transporter for which P i (40) or arsenate (48) can serve as the anion (39). Additionally, several organophosphate transport systems result in P i uptake in E. coli (42).Recently, the genes encoding proteins homologous to those of the E. coli pst gene products were cloned and sequenced in Bacillus subtilis (36). Five cistrons with homology to genes in the E. coli pst operon were named pstS, pstC, pstA, pstB1, and pstB2. A putative promoter sequence was located 5Ј of the pstS gene, and a potential rho-independent transcription terminator (⌬G ϭ Ϫ18.4 kcal/mol) was observed 3Ј of pstB2.The pst operon of E. coli and the proposed pst operon of B. subtilis encode proteins similar to ABC transporters (3, 45), which are composed of a binding protein (similar to PstS), two integral inner membrane proteins (similar to PstC and PstA), and an ATP binding protein (similar to PstB for E. coli or PstB1 and PstB2 for B. subtilis). The pstB2 gene is at the 3Ј end of the operon in the position of phoU in E. coli. PhoU, which has no similarity to ABC proteins, is not in the pst operon of B. subtilis.The first four genes in the pst operon of E. coli, i.e., pstS, pstC, pstA, and pstB, are required for phosphate transport; mutations in any of these genes abolish P i uptake (6,33,46) when the concentration of P i is low. The pst operon also has a role in the regulation of Pho regulon genes (1,43,46) in that phoU is required for the repression of the Pho regulon but is apparently not required for phosphate transport through the Pst system (25,34,50).E. coli genes induced by phosphate starvation and controlled by phoB-phoR constitute the Pho regulon (21,22,37,38,41). During P i limitation, PhoR (histidine kinase) turns on the Pho regulon genes by phosphorylating PhoB, a response regulator. The activated phoB in turn activates transcription by binding specifically to a DNA sequence of 18 nucleotides (the Pho box) (20), which is part of the promoter of each Pho regulon gene, including the pst operon.In B. subtilis, Pho regulon genes are exp...

Post-transcriptional regulation of the Bacillus subtilis pst operon encoding a phosphate-specific ABC transporter

“…Using a combination of reporter gene and DNA array technology, we have shown that pit expression is independent of P i concentration and PhoPR (N. E. E. Allenby, C. R. Harwood & Z. Prágai, unpublished). In contrast, the pst operon is induced specifically in response to P i starvation in a PhoPdependent manner (Qi et al, 1997). The products of this operon form the main transporter of phosphate at low P i concentrations (<0?1 mM) and pst mutants exhibit an approximately sevenfold reduction in P i uptake under these conditions (Prágai et al, 2001).…”

“…The pst operon is transcribed from a sigma A-type promoter located immediately upstream of pstS (Qi et al, 1997). Recently, the operon has been shown to be induced during alkali stress (Atalla & Schumann, 2003).…”

Sites internal to the coding regions of phoA and pstS bind PhoP and are required for full promoter activity

“…The cell also secretes multiple alkaline phosphatases (APases) Hulett, 1993;1995;1996), alkaline phosphodiesterases (Le Hegarat and Anagnostopoulos, 1973;Yamane and Maruo, 1978a,b;Eder et al, 1996) and other hydrolytic enzymes (Kusser and Fiedler, 1982;1983) to recycle the available phosphorus from teichoic acid (Grant, 1979). The inorganic phosphate produced in this process is then transferred into the cell by an efficient high-affinity phosphate transport system (Eymann et al, 1996;Qi et al, 1997). Some of the genes that are involved in this process, the Pho regulon genes, have been cloned, and their promoter activities have been found to be regulated by two regulatory genes, phoP and phoR, under phosphate starvation conditions Hulett et al, 1990;1994a,b;Chesnut et al, 1991;Eder et al, 1996;Qi et al, 1997).…”

“…The inorganic phosphate produced in this process is then transferred into the cell by an efficient high-affinity phosphate transport system (Eymann et al, 1996;Qi et al, 1997). Some of the genes that are involved in this process, the Pho regulon genes, have been cloned, and their promoter activities have been found to be regulated by two regulatory genes, phoP and phoR, under phosphate starvation conditions Hulett et al, 1990;1994a,b;Chesnut et al, 1991;Eder et al, 1996;Qi et al, 1997).…”

Phosphate Acquisition Components of the Myxococcus xanthus Pho Regulon Are Regulated by both Phosphate Availability and Development

“…This might be the case if polyphosphate acts as an alarmone signal for activation of the Lon protease rather than as a phosphate storage molecule in M. xanthus, as suggested by Zhang et al (24). In B. subtilis pstSCAB promoter activity is induced ϳ5,000-fold upon P limitation, from ϳ0 to ϳ4,500 U of LacZ (18). In contrast, P limitation in M. xanthus increases the pstSCAB promoter activity from ϳ150 to ϳ650 U of LacZ (Fig.…”