HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Gebhard, S. Articles by Cook, G. M. Search for Related Content PubMed PubMed Citation Articles by Gebhard, S. Articles by Cook, G. M. Agricola Articles by Gebhard, S. Articles by Cook, G. M.

The Phn system of Mycobacterium smegmatis: a second high-affinity ABC-transporter for phosphate

Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, PO Box 56, Dunedin, New Zealand

Correspondence
Gregory M. Cook
greg.cook{at}stonebow.otago.ac.nz

Uptake of inorganic phosphate, an essential but often limiting nutrient, in bacteria is usually accomplished by the high-affinity ABC-transport system Pst. Pathogenic species of mycobacteria contain several copies of the genes encoding the Pst system (pstSCAB), and two of the encoded proteins, PstS1 and PstS2, have been shown to be virulence factors in Mycobacterium tuberculosis. The fast-growing Mycobacterium smegmatis contains only a single copy of the pst operon. This study reports the biochemical and molecular characterization of a second high-affinity phosphate transport system, designated Phn. The Phn system is encoded by a three-gene operon that constitutes the components of a putative ABC-type phosphonate/phosphate transport system. Expression studies using phnD– and pstS–lacZ transcriptional fusions showed that both operons were induced when the culture entered phosphate limitation, indicating a role for both systems in phosphate uptake at low extracellular concentrations. Deletion mutants in either phnD or pstS failed to grow in minimal medium with a 10 mM phosphate concentration, while the isogenic wild-type strain mc²155 grew at micromolar phosphate concentrations. Analysis of the kinetics of phosphate transport in the wild-type and mutant strains led to the proposal that the Phn and Pst systems are both high-affinity phosphate transporters with similar affinities for phosphate (i.e. apparent K_m values between 40 and 90 µM P_i). The Phn system of M. smegmatis appears to be unique in that, unlike previously identified Phn systems, it does not recognize phosphonates or phosphite as substrates.

This article has been cited by other articles:

				J. C. Gauntlett, S. Gebhard, S. Keis, J. M. Manson, K. M. Pos, and G. M. Cook Molecular Analysis of BcrR, a Membrane-bound Bacitracin Sensor and DNA-binding Protein from Enterococcus faecalis J. Biol. Chem., March 28, 2008; 283(13): 8591 - 8600. [Abstract] [Full Text] [PDF]

				M. Niederweis Nutrient acquisition by mycobacteria Microbiology, March 1, 2008; 154(3): 679 - 692. [Abstract] [Full Text] [PDF]

				S. Gebhard and G. M. Cook Differential Regulation of High-Affinity Phosphate Transport Systems of Mycobacterium smegmatis: Identification of PhnF, a Repressor of the phnDCE Operon J. Bacteriol., February 15, 2008; 190(4): 1335 - 1343. [Abstract] [Full Text] [PDF]