Regulation of the Escherichia coli lrp gene

Abstract

Lrp (leucine-responsive regulatory protein) is a major Escherichia coli regulatory protein which regulates expression of a number of operons, some negatively and some positively. Operons that are affected by the presence or absence of Lrp includefanABC (3), gcv (10), ginA (5), gltBD (5), ilvIH (20), livJ and livK (7), lysU (6, 11), ompC and ompF (5), oppABCDF (1), papBA (3), sdaA (12), serA (12, 21), and tdh (12, 21). Some of these operons (e.g., ilvIH) are known to be directly controlled by Lrp, whereas others (e.g., ginA) are affected only indirectly by Lrp. Other operons that are affected by Lrp were identified by a plac Mu mutational analysis and by two-dimensional gel electrophoresis (5, 10). Many operons under control of Lrp are also subject to control by leucine. A striking feature of the Lrp regulon is the variety of ways that leucine and Lrp interact to regulate gene expression (16). Of the operons activated by Lrp, in some cases the activation requires leucine, in some cases the activation is negated by leucine, and in other cases the activation is independent of leucine. Similarly, for operons which are negatively regulated by Lrp, the same three subcategories have been observed: leucine negates the effect, leucine is required for the effect, and leucine has no effect. The molecular mechanisms underlying these six different patterns of regulation involving Lrp and leucine are only partially understood.Lrp, a dimer containing two identical subunits of molecular mass 18.8 kDa, is present in E. coli at a level of about 3,000 molecules per cell (32). Its amino acid sequence is evolutionarily related to that of AsnC, a regulatory protein that controls

Defining a rob Regulon in Escherichia coli by Using Transposon Mutagenesis

“…Insertions mb17 and mb55 were both located in ybaO. This gene codes for a predicted protein that has a strong similarity to leucine-responsive regulatory protein (Lrp) from E. coli and to Lrp homologs in several other bacteria (25,34). Insertion mb83 mapped in mdlA, directly downstream of ybaO.…”

Growth phase‐dependent expression and degradation of histones in the thermophilic archaeon Thermococcus zilligii

“…The LRPs are major transcriptional regulators found in both Archaea and Bacteria. In E. coli, LRPs control the expression of a large number of operons, can act as both repressers and activators and are suggested to be involved in chromosomal organization (Lin et al, 1992;Wang et al, 1994). Curiously, SRDTz corresponds to only the C-terminal half of the LRPs.…”

Metabolic regulation of Irp gene expression in Escherichia coli K-12

“…Lrp cannot be considered to regulate expression of these genes unless Lrp expression itself varies, or Lrp has effector(s) other than leucine (D'Ari et al, 1993). Autogenous repression of lrp expression by Lrp itself has been previously described Wang et al, 1994) and depends on Lrp binding to well-characterized sites upstream of the coding sequence (Wang et al, 1994). However, there is also a strong metabolic effect on Lrp expression which does not depend on the Lrp molecule as shown by the fact that a strain carrying .…”

“…In this paper, we demonstrate a number of metabolic factors influencing the expression of the Zrp gene in E. coli K-12. footprinting, and mutation and deletion studies (Wang et al, 1994). In the metabolic regulation system, neither a signalling molecule(s) nor its effector has been identified.…”