Genetic mapping off fructose-1,6-diphosphatase in Escherichia coli

Isolation of a Mutant of Escherichia coli with a Temperature-sensitive Fructose-1,6-Diphosphate Aldolase Activity

Böck, August (Purdue University, Lafayette, Ind.), and Frederick C. Neidhardt. Isolation of a mutant of Escherichia coli with a temperature-sensitive fructose-1,6-diphosphate aldolase activity. J. Bacteriol. 92:464-469. 1966.-A mutant of Escherichia coli was isolated which was able to grow in rich medium at 30 C but not at 40 C. Upon exposure to 40 C, the cells immediately stopped ribonucleic acid (RNA) and deoxyribonucleic acid synthesis, but protein synthesis continued at a diminished rate for a short time. Addition of chloramphenicol did not release RNA synthesis from inhibition at 40 C. Synthesis of beta-galactosidase could be induced at high temperature despite the presence of glucose in the medium, indicating a lesion in glucose catabolism. Of many catabolic enzymes tested in cell-free extracts, only fructose-1,6-diphosphate aldolase activity appeared to be altered in the mutant cells. No activity was demonstrable in extracts of mutant cells grown at either 30 or 40 C, but determination of glucose-oxidation patterns revealed that the enzyme is probably active in vivo at 30 C. Temperature-resistant secondary mutants were found to have partially or fully restored aldolase activity, and temperature-resistant recombinants had normal aldolase activity, indicating that the growth pattern and the altered aldolase had a common genetic basis. Linkage data permitted the assignment of an approximate map location for the mutated aldolase gene.

Identification and expression of the Bacillus subtilis fructose-1, 6-bisphosphatase gene (fbp)

The Bacillus subtilis fbp gene encoding fructose-1,6-bisphosphatase (FBPase) was originally identified as yydE. The fbp gene was expressed at a fairly constant level in cells undergoing glycolysis or gluconeogenesis. fbp transcription was initiated 94 bp upstream of the translation initiation codon, resulting in a 2.4-kb monocistronic transcript. Interestingly, B. subtilis FBPase exhibited no significant similarity to other FBPases in protein sequence databases.

Isolation and properties of a Bacillus subtilis mutant unable to produce fructose-bisphosphatase

A Bacillus subtilis mutation (gene symbol fdpA1), producing a deficiency of D-fructose-1,6-bisphosphate 1-phosphohydrolase (EC 3.1.3.11, fructose-bisphosphatase), was isolated and genetically purified. An fdpA1-containing mutant did not produce cross-reacting material. It grew on any carbon source that allowed growth of the standard strain except myo-inositol and D-gluconate. Because the mutant could grow on D-fructose, glycerol, or L-malate as the sole carbon source, B. subtilis can produce fructose-6-phosphate and the derived cell wall precursors from these carbon sources in the absence of fructose-bisphosphatase. In other words, during gluconeogenesis B. subtilis must be able to bypass this reaction. Fructose-bisphosphatase is also not needed for the sporulation of B., subtilis. The fdpA1 mutation has the pleiotropic consequence that mutants carrying it cannot produce inositol dehydrogenase (EC 1.1.1.18) and gluconate kinase (EC 2.7.1.12) under conditions that normally induce these enzymes.

Quaternary constraint in hybrid of aspartate transcarbamylase containing wild-type and mutant catalytic subunits

Unusual quaternary constraint in the regulatory enzyme, aspartate transcarbamylase (aspartate carbamoyltransferase or carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) from Escherichia coli, was demonstrated with a hybrid composed of one inactive "catalytic" subunit from a mutant strain and one active catalytic subunit and three regulatory subunits from the wild-type strain. The hybrid had a high affinity for three molecules of the bi-substrat analog, N-(phosphonacetyl)-L-aspartate, compared to the six strong binding sites in the wild-type enzyme and none in the mutant. However, the Vmax of the hybrid was only about 25% that of the wild-type enzyme. In addition, the hybrid exhibited a very low apparent affinity for the substrate, aspartate [Michaelis constant (Km) about 90 mM], as compared to the wild-type enzyme (apparent Km of 7 mM). No homotropic effect was observed for the hybrid in the absence of nucleotides as contrasted to the cooperativity of the wild-type enzyme; also, large changes in the Vmax of the hybrid were caused by the addition of the nucleotide effectors, CTP and ATP, which do not affect the Vmax of the wild-type, but influence only the cooperativity and the apparent Km. Although the hybrid undergoes a ligand-promoted conformational change analogous to that of the wild-type enzyme, this transition required a 20-fold higher concentration of the substrate analog, succinate. It appears that the "paralysis" of the wild-type catalytic subunit in the hybrid can be attributed to subunit interactions which constrain the molecule in a low-affinity state.

Incompatibility of integrated sex factors in double male strains of Escherichia coli

Several strains of Escherichia coli K-12 harboring two F factors were isolated from Hfr x Hfr crosses. These strains were transiently capable of initiating chromosome transfer from two separate points of origin, and of transferring two different sex factors as integrated chromosomal markers. Each strain tested invariably reverted to a simple Hfr by loss of one of the inherited F factors. The F factor persisting in the revertant was, in nearly every case, that which had been inherited from the recipient Hfr parent.

Genetic mapping of mutations affecting phosphoglucose isomerase and fructose diphosphatase in Escherichia coli

The loci on the Escherichia coli genome of mutations affecting phosphoglucose isomerase (pgi) and fructose diphosphatase (fdp) have been determined by conjugation and transduction experiments, chiefly three-factor crosses. The loci for these two constitutive enzymes of central intermediary metabolism lie in the same region of the chromosome, but they are not cotransducible. The order of some markers in this region of the chromosome is arg(ACFH) metA pgi malB uvrA fdp pyrB thr.

Fructose-1, 6-diphosphatase and acid hexose phosphatase of Escherichia coli

Fraenkel, D. G. (Albert Einstein College of Medicine, New York, N.Y.), and B. L. Horecker. Fructose-1,6-diphosphatase and acid hexose phosphatase of Escherichia coli. J. Bacteriol. 90:837-842. 1965.-The conversion of fructose-1,6-diphosphate to fructose-6-phosphate (fructose-1,6-diphosphatase activity) is essential for growth of Escherichia coli on glycerol, acetate, or succinate, but is unnecessary for growth on hexoses or pentoses. It has sometimes been assumed that fructose-1,6-diphosphatase activity is due to a nonspecific acid hexose phosphatase. We have now obtained a number of one-step mutants which have lost the ability to grow on glycerol, succinate, or acetate, but which grow normally on hexoses; these mutants are deficient in a fructose-1,6-diphosphatase which can be assayed spectrophotometrically in the presence of Mg(++) and low concentrations of substrate. These mutants still possess the nonspecific acid hexose phosphatase, which does not require Mg(++) and is active only at much higher concentrations of fructose-1,6-diphosphate. Evidence is presented to support the hypothesis that the newly described activity is the physiological fructose-1,6-diphosphatase. The acid hexose phosphatase is a different enzyme whose function remains unknown.