Two different mechanisms mediate catabolite repression of the Bacillus subtilis levanase operon

J Bacteriol. 1995 Dec;177(23):6919-27. doi: 10.1128/jb.177.23.6919-6927.1995.

Abstract

There are two levels of control of the expression of the levanase operon in Bacillus subtilis: induction by fructose, which involves a positive regulator, LevR, and the fructose phosphotransferase system encoded by this operon (lev-PTS), and a global regulation, catabolite repression. The LevR activator interacts with its target, the upstream activating sequence (UAS), to stimulate the transcription of the E sigma L complex bound at the "-12, -24" promoter. Levanase operon expression in the presence of glucose was tested in strains carrying a ccpA gene disruption or a ptsH1 mutation in which Ser-46 of HPr is replaced by Ala. In a levR+ inducible genetic background, the expression of the levanase operon was partially resistant to catabolite repression in both mutants, indicating that the CcpA repressor and the HPr-SerP protein are involved in the glucose control of this operon. In addition, a cis-acting catabolite-responsive element (CRE) of the levanase operon was identified and investigated by site-directed mutagenesis. The CRE sequence TGAAAACGCTT(a)ACA is located between positions -50 and -36 from the transcriptional start site, between the UAS and the -12, -24 promoter. However, in a background constitutive for levanase, neither HPr, CcpA, nor CRE is involved in glucose repression, suggesting the existence of a different pathway of glucose regulation. Using truncated LevR proteins, we showed that this CcpA-independent pathway required the presence of the domain of LevR (amino acids 411 to 689) homologous to the BglG family of bacterial antiterminators.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / enzymology
  • Bacillus subtilis / genetics*
  • Bacterial Proteins / genetics
  • Base Sequence
  • DNA-Binding Proteins / metabolism
  • Enzyme Induction
  • Enzyme Repression
  • Gene Expression Regulation, Bacterial*
  • Genes, Bacterial
  • Glucose / pharmacology
  • Glycoside Hydrolases / genetics*
  • Models, Genetic
  • Molecular Sequence Data
  • Mutation
  • Operon*
  • Phosphoenolpyruvate Sugar Phosphotransferase System / metabolism
  • Regulatory Sequences, Nucleic Acid
  • Repressor Proteins / metabolism
  • Sequence Deletion
  • Signal Transduction
  • Transcription Factors / genetics

Substances

  • Bacterial Proteins
  • DNA-Binding Proteins
  • Repressor Proteins
  • Transcription Factors
  • catabolite control proteins, bacteria
  • LevR protein, Bacillus subtilis
  • Phosphoenolpyruvate Sugar Phosphotransferase System
  • phosphocarrier protein HPr
  • Glycoside Hydrolases
  • levanase
  • Glucose