Lysine represses transcription of the Escherichia coli dapB gene by preventing its activation by the ArgP activator

J Bacteriol. 2008 Aug;190(15):5224-9. doi: 10.1128/JB.01782-07. Epub 2008 May 23.

Abstract

The Escherichia coli dapB gene encodes one of the enzymes of the biosynthetic pathway leading to lysine and its immediate precursor, diaminopimelate. Expression of dapB is repressed by lysine, but no trans-acting regulator has been identified so far. Our analysis of the dapB regulatory region shows that sequences located in the -81/-118 interval upstream of the transcription start site are essential for full expression of dapB, as well as for lysine repression. Screening a genomic library for a gene that could alleviate lysine repression when present in multicopy led to the recovery of argP, a gene encoding an activating protein of the LysR-type family, known to use lysine as an effector. An argP null mutation strongly decreases dapB transcription that becomes insensitive to lysine. Purified His(6)-tagged ArgP protein binds with an apparent K(d) of 35 nM to the dapB promoter in a gel retardation assay, provided that sequences up to -103 are present. In the presence of L-lysine and L-arginine, the binding of ArgP to dapB is partly relieved. These results fit with a model in which ArgP contributes to enhanced transcription of dapB when lysine becomes limiting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arginine / metabolism
  • Artificial Gene Fusion
  • Base Sequence
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / isolation & purification
  • DNA-Binding Proteins / metabolism*
  • Dihydrodipicolinate Reductase / biosynthesis*
  • Electrophoretic Mobility Shift Assay
  • Escherichia coli / enzymology
  • Escherichia coli / physiology*
  • Escherichia coli Proteins / biosynthesis*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / isolation & purification
  • Escherichia coli Proteins / metabolism
  • Gene Deletion
  • Gene Expression Regulation, Bacterial*
  • Genes, Reporter
  • Lysine / metabolism*
  • Molecular Sequence Data
  • Promoter Regions, Genetic
  • Protein Binding
  • Regulatory Sequences, Nucleic Acid
  • Transcription, Genetic
  • beta-Galactosidase / biosynthesis
  • beta-Galactosidase / genetics

Substances

  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • argP protein, E coli
  • Arginine
  • Dihydrodipicolinate Reductase
  • beta-Galactosidase
  • Lysine