Sinorhizobium meliloti putA gene regulation: a new model within the family Rhizobiaceae.
Proline dehydrogenase (PutA) is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate. In Sinorhizobium meliloti, as in other microorganisms, the putA gene is transcriptionally activated in response to proline. In Rhodobacter capsulatus, Agrobacterium, and most probably in Bradyrhizobium, this activation is dependent on an Lrp-like protein encoded by the putR gene, located immediately upstream of putA. Interestingly, sequence and genetic analysis of the region upstream of the S. meliloti putA gene did not reveal such a putR locus or any other encoded transcriptional activator of putA. Furthermore, results obtained with an S. meliloti putA null mutation indicate the absence of any proline-responsive transcriptional activator and that PutA serves as an autogenous repressor. Therefore, the model of S. meliloti putA regulation completely diverges from that of its Rhizobiaceae relatives and resembles more that of enteric bacteria. However, some differences have been found with the latter model: (i) S. meliloti putA gene is not catabolite repressed, and (ii) the gene encoding for the major proline permease (putP) does not form part of an operon with the putA gene.
Soto
M J
MJ
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain.
Jiménez-Zurdo
J I
JI
van Dillewijn
P
P
Toro
N
N
D026921:Amino Acid Transport Systems, Neutral; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D005947:Glucose / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics; D011392:Proline / Q000494:pharmacology; D011394:Proline Oxidase / Q000235:genetics* / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D017384:Sequence Deletion / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D015534:Trans-Activators
D026921:Amino Acid Transport Systems, Neutral; D001426:Bacterial Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C080683:PutA protein, Bacteria; C096745:PutR protein, Bacteria; D012097:Repressor Proteins; D015534:Trans-Activators; C033082:proline transporter; D011392:Proline; D011394:Proline Oxidase; D005947:Glucose