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Tandem attenuators control expression of the Salmonella mgtCBR virulence operon
Author(s) -
Lee EunJin,
Groisman Eduardo A.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08188.x
Subject(s) - biology , operon , open reading frame , orfs , transcription (linguistics) , genetics , stringent response , salmonella enterica , coding region , proline , start codon , reading frame , messenger rna , amino acid , salmonella , gene , peptide sequence , mutant , bacteria , linguistics , philosophy
Summary The mgtCBR operon from Salmonella enterica serovar Typhimurium specifies the virulence protein MgtC, the Mg 2+ transporter MgtB and the regulatory peptide MgtR. The mgtCBR transcript includes a long leader region harbouring two short open reading frames (ORFs). Translation of these ORFs is anticipated to impact the formation of particular stem‐loop structures and control transcription of the coding region by an attenuation‐like mechanism. We previously reported that ORF mgtM enables Salmonella to promote transcription of the mgtC and mgtB coding regions when experiencing a rise in cytoplasmic ATP levels. We now show that the proline codon‐rich ORF mgtP mediates an increase in transcription of the mgtC and mgtB coding regions under conditions predicted to decrease the levels of proline‐charged tRNA Pro . The high ATP and low proline signals act independently in an additive form. Replacing conserved mgtP proline codons with codons specifying other amino acids abolished the response to proline limitation but had no effect on the response to ATP. Substitution of conserved adenine nucleotides in mgtM abolished the response to ATP but had no effect in the response to proline limitation. This provides a singular example of a leader mRNA with tandem attenuators responding to different signals.