Co-ordinated Regulation of Amino Sugar Biosynthesis and Degradation: The NagC Repressor Acts as Both an Activator and a Repressor for the Transcription of the glmUS Operon and Requires Two Separated NagC Binding Sites

EMBO J. 1995 Aug 15;14(16):3958-65.


The NagC repressor controls the expression of the divergently transcribed nagE-nagBACD operons involved in the uptake and degradation of the amino sugars, N-acetyl-D-glucosamine (GlcNAc) and glucosamine (GlcN). The glmUS operon, encoding proteins necessary for the synthesis of GlcN (glmS) and the formation of UDP-GlcNAc (glmU), is transcribed from two promoters located upstream of glmU. In the absence of amino sugars both promoters are active. However, in the presence of GlcNAc, the glmU proximal promoter, P1, is inactive while the upstream promoter, P2, is subject to weak induction. Two binding sites for the NagC repressor are located at -200 and -47 bp upstream of P1. Mutations which prevent NagC binding to either of these sites eliminate expression from the P1 promoter. This shows that binding of NagC is necessary for expression of the glmU P1 promoter and implies that NagC is playing the role of activator for this promoter. Moreover, the location of the distal NagC site suggests that this site is behaving like an upstream activating sequence (UAS).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylglucosamine / biosynthesis
  • Acetylglucosamine / metabolism
  • Amino Sugars / biosynthesis*
  • Amino Sugars / metabolism
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bacterial Proteins / physiology
  • Base Sequence
  • DNA, Bacterial / metabolism
  • Enzyme Repression
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial / genetics*
  • Glucosamine / biosynthesis
  • Glucosamine / metabolism
  • Molecular Sequence Data
  • Mutation
  • Nucleotidyltransferases / biosynthesis
  • Nucleotidyltransferases / genetics*
  • Operator Regions, Genetic / genetics
  • Operon / genetics
  • Promoter Regions, Genetic / genetics
  • RNA, Bacterial / biosynthesis
  • RNA, Messenger / biosynthesis
  • Recombinant Fusion Proteins / biosynthesis
  • Repressor Proteins / metabolism*
  • Repressor Proteins / physiology
  • Trans-Activators / metabolism*
  • Trans-Activators / physiology
  • Transcription Factors*
  • Transcription, Genetic / genetics*


  • Amino Sugars
  • Bacterial Proteins
  • DNA, Bacterial
  • Escherichia coli Proteins
  • RNA, Bacterial
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • Repressor Proteins
  • Trans-Activators
  • Transcription Factors
  • component S, glutamate mutase protein, Bacteria
  • nagC protein, E coli
  • Nucleotidyltransferases
  • UDPacetylglucosamine pyrophosphorylase
  • Glucosamine
  • Acetylglucosamine

Associated data

  • GENBANK/S79444