Mu-induced polarity in the Escherichia coli K-12 ent gene cluster: evidence for a gene (entG) involved in the biosynthesis of enterochelin

Abstract

A strain of Escherichia coli K-12 has been isolated that carries a Mu bacteriophage-induced mutation in the ent gene cluster. Nutritional tests together with examination of the compounds accumulated by the mutant strain indicated that the mutant was blocked both in the synthesis of 2,3-dihydroxybenzoate and its subsequent conversion into enterochelin. Enzymic complementation assays of the mutant with several mutants each affected in one of the ent genes showed that the Mu-induced mutant was entA-, entBf, entC+, entD+, entE+, and entF+. Since the mutant produced the entD, entE, and entF gene products but was unable to produce enterochelin from 2,3-dihydroxybenzoate, it must therefore be affected in an additional protein concerned with this conversion. It is therefore postulated that the Mu-induced mutation affects a previously unrecognized gene, entG. Genetic experiments indicate that the mutation in strain AN462 which affects the three ent genes is the result of a single insertion of Mu in the ent gene cluster. This polarity mutant therefore provides evidence that three of the ent genes are part of an operon.

Molecular studies on enzymes in chorismate metabolism and the enterobactin biosynthetic pathway

“…A further mutation in enterobactin biosynthesis, entG, was identified with use of bacteriophage Mu-induced mutagenesis and postulated to affect the conversion of 2,3-dihydroxybenzoate to enterobactin. 87 The significance of the entG mutation will be discussed in section III.D.…”

Enterobactin Synthase Polypeptides of Escherichia Coli are Present in an Osmotic-Shock-Sensitive Cytoplasmic Locality

“…EntB/G and EntD are essential but their roles have not been determined. Ent B/G (32·5 kDa) seems to be a bifunctional protein (Staab & Earhart, 1990) required both for an early step in Ent biosynthesis (EntB activity; Rusnak et al, 1990) and an unidentified later step (EntG activity) (Greenwood & Luke, 1976, 1980; Woodrow et al, 1975); the early and late synthetic activities of Ent B/G are separable by mutation and appear to reside in the N- and C-termini of the protein, respectively. That EntB and EntG activities are on the same polypeptide is supported by the detection (unpublished results) of homology between the C-terminus of EntB/G and the N-terminus of iron-regulated HMWP2 of Yersinia enterocolitica (Guilvout et al, 1993); the homologous regions include a consensus substrate amino acid binding site for enzymes engaged in non-ribosomal peptide synthesis (Schlumbohm et al, 1991).…”

Regulation of enterobactin iron transport in Escherichia coli: characterization of ent::Mu d(Apr lac) operon fusions

“…From a common intermediate of aromatic amino acid synthesis, the enterobactin biosynthesis genes entC, entB, and entA convert chorismate to 2,3-hihydroxybenzoic acid (32). 2,3-Dihydroxybenzoic acid and Lserine are substrates for the production of enterobactin by enterobactin synthetase, which is composed of four enzymes, the products of entD, entE, entF, and entG (20,29). Release of the siderophore into the medium occurs by an uncharacterized mechanism.…”

“…Laird et al (16) observed that the enterobactin cistrons span approximately 29 kilobases of DNA and are organized in the following order: entD, fes, entF, fep, and ent(CA)GBE. Thefep mutations used in this study all fell into the same complementation group now defined as fepB (21).…”