Bacillus subtilis ilvB operon: an intersection of global regulons

• Published in: Molecular microbiology Vol. 56; no. 6; pp. 1549 - 1559
• Main Authors: Shivers, Robert P., Sonenshein, Abraham L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.2005; Blackwell Science; Blackwell Publishing Ltd
• Subjects: Amino acids; Bacillus subtilis - genetics; Bacillus subtilis - metabolism; Bacteria; Bacterial proteins; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; Biological and medical sciences; Biosynthesis; Chemical synthesis; DNA Footprinting; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Isoleucine - metabolism; Microbiology; Molecular Sequence Data; Operon; Promoter Regions, Genetic; Regulon - genetics; Regulon - physiology; Repressor Proteins - genetics; Repressor Proteins - metabolism; Transcription, Genetic; Valine - metabolism; Bacteria; Bacillales; Microbiology; Bacillaceae; Bacillus subtilis; Operon
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2005.04634.x

Summary The genes of the major Bacillus subtilis operon (ilvB) for biosynthesis of branched‐chain amino acids are subject to multiple mechanisms of regulation. The global regulatory proteins CodY and TnrA bind upstream of the transcription start site and are likely to control transcription initiation, leucine‐specific tRNA regulates transcriptional elongation, and unknown factors differentially cleave the full‐length mRNA. Another global regulator, CcpA, known to be required for ilvB transcription, was shown here to act directly at the ilvB promoter by a novel mechanism. Although CcpA was able to bind to the ilvB promoter region, it stimulated transcription significantly only when CodY was present, suggesting that CcpA acts primarily by interfering with repression by CodY. Additionally, CcpA was shown to control indirectly the expression of other CodY‐regulated target genes, apparently by altering the intracellular level of branched‐chain amino acids.