title: Proline utilization by Bacillus subtilis: uptake and catabolism.
abstract: L-Proline can be used by Bacillus subtilis as a sole source of carbon or nitrogen. We traced L-proline utilization genetically to the putBCP (ycgMNO) locus. The putBCP gene cluster encodes a high-affinity proline transporter (PutP) and two enzymes, the proline dehydrogenase PutB and the Δ(1)-pyrroline-5-carboxylate dehydrogenase PutC, which jointly catabolize L-proline to L-glutamate. Northern blotting, primer extension, and putB-treA reporter gene fusion analysis showed that the putBCP locus is transcribed as an L-proline-inducible operon. Its expression was mediated by a SigA-type promoter and was dependent on the proline-responsive PutR activator protein. Induction of putBCP expression was triggered by the presence of submillimolar concentrations of L-proline in the growth medium. However, the very large quantities of L-proline (up to several hundred millimolar) synthesized by B. subtilis as a stress protectant against high osmolarity did not induce putBCP transcription. Induction of putBCP transcription by external L-proline was not dependent on L-proline uptake via the substrate-inducible PutP or the osmotically inducible OpuE transporter. It was also not dependent on the chemoreceptor protein McpC required for chemotaxis toward L-proline. Our findings imply that B. subtilis can distinguish externally supplied L-proline from internal L-proline pools generated through de novo synthesis. The molecular basis of this regulatory phenomenon is not understood. However, it provides the B. subtilis cell with a means to avoid a futile cycle of de novo L-proline synthesis and consumption by not triggering the expression of the putBCP L-proline catabolic genes in response to the osmoadaptive production of the compatible solute L-proline.
authors.affiliation: Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Marburg, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Moses
authors.forename: Tatjana
authors.initials: T
authors.lastname: Sinner
authors.forename: Adrienne
authors.initials: A
authors.lastname: Zaprasis
authors.forename: Nadine
authors.initials: N
authors.lastname: Stöveken
authors.forename: Tamara
authors.initials: T
authors.lastname: Hoffmann
authors.forename: Boris R
authors.initials: BR
authors.lastname: Belitsky
authors.forename: Abraham L
authors.initials: AL
authors.lastname: Sonenshein
authors.forename: Erhard
authors.initials: E
authors.lastname: Bremer
mesh_terms: D050842:1-Pyrroline-5-Carboxylate Dehydrogenase / Q000378:metabolism; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017930:Genes, Reporter; D018698:Glutamic Acid / Q000378:metabolism; D009876:Operon; D011392:Proline / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D018698:Glutamic Acid; C033082:proline transporter; D011392:Proline; D050842:1-Pyrroline-5-Carboxylate Dehydrogenase