title: Salmonella typhimurium PtsJ is a novel MocR-like transcriptional repressor involved in regulating the vitamin B6salvage pathway.
abstract: The vitamin B6salvage pathway, involving pyridoxine 5'-phosphate oxidase (PNPOx) and pyridoxal kinase (PLK), recycles B6vitamers from nutrients and protein turnover to produce pyridoxal 5'-phosphate (PLP), the catalytically active form of the vitamin. Regulation of this pathway, widespread in living organisms including humans and many bacteria, is very important to vitamin B6homeostasis but poorly understood. Although some information is available on the enzymatic regulation of PNPOx and PLK, little is known on their regulation at the transcriptional level. In the present work, we identified a new MocR-like regulator, PtsJ from Salmonella typhimurium, which controls the expression of the pdxK gene encoding one of the two PLKs expressed in this organism (PLK1). Analysis of pdxK expression in a ptsJ knockout strain demonstrated that PtsJ acts as a transcriptional repressor. This is the first case of a MocR-like regulator acting as repressor of its target gene. Expression and purification of PtsJ allowed a detailed characterisation of its effector and DNA-binding properties. PLP is the only B6vitamer acting as effector molecule for PtsJ. A DNA-binding region composed of four repeated nucleotide sequences is responsible for binding of PtsJ to its target promoter. Analysis of binding stoichiometry revealed that protein subunits/DNA molar ratio varies from 4 : 1 to 2 : 1, depending on the presence or absence of PLP. Structural characteristics of DNA transcriptional factor-binding sites suggest that PtsJ binds DNA according to a different model with respect to other characterised members of the MocR subgroup.
authors.affiliation: Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Rome, Italy.|Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Tramonti
authors.affiliation: Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Milano
authors.affiliation: Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Nardella
authors.affiliation: Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Martino L
authors.initials: ML
authors.lastname: di Salvo
authors.affiliation: Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Pascarella
authors.affiliation: Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Sapienza Università di Roma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Contestabile
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011731:Pyridoxal Kinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000737:chemistry / Q000378:metabolism; D011734:Pyridoxaminephosphate Oxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D014158:Transcription, Genetic; D025101:Vitamin B 6 / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011994:Recombinant Proteins; D012097:Repressor Proteins; D011732:Pyridoxal Phosphate; D025101:Vitamin B 6; D011734:Pyridoxaminephosphate Oxidase; D011731:Pyridoxal Kinase
keywords: 
  Salmonella typhimurium
  ; MocR; PtsJ; pyridoxal kinase; vitamin B6 salvage pathway