Synthesis of quinolinate from D-aspartate in the mammalian liver-Escherichia coli quinolinate synthetase system.

Two proteins (A and B) from $\text{Escherichia coli}$ are required for the synthesis of the NAD precursor quinolinate from aspartate and dihydroxyacetone phosphate. Mammalian liver contains a FAD linked protein which replaces $\text{E. coli}$ B protein for quinolinate synthesis. D-aspartic acid but not L-aspartic acid is a substrate for quinolinic acid synthesis in a system composed of the B protein replacing activity of mammalian liver and $\text{E. coli}$ A protein. In contrast the $\text{E. coli}$ B protein-$\text{E. coli}$ A protein quinolinate synthetase system requires L-aspartic acid as substrate. The previous report that L-aspartate was a substrate in the liver-$\text{E. coli}$ system was due to contamination of commercially available [¹⁴C]L-aspartate with [¹⁴C]D-aspartate. These and other observations suggest that liver B protein is D-aspartate oxidase and $\text{E. coli}$ B protein is L-aspartate oxidase.     

Occurrence in mammalian liver of a protein which replaces the B protein of E. coli quinolinate synthetase.

$\text{Escherichia coli}$ contains two proteins (A and B) which together convert dihydroxyacetone phosphate and aspartate to quinolinic acid, a precursor of NAD. Although mammalian liver homogenate does not catalyze this reaction it contains a protein which will replace the B protein of the $\text{E. coli}$ system. The behavior of the liver protein on Sephadex G-75 suggests it is much smaller than the $\text{E. coli}$ B protein. Liver B protein also appears to contain tightly bound FAD while FAD is easily removed from the $\text{E. coli}$ B protein. The pH optimum for the hybrid system $\text{E. coli}$ A protein-liver B protein is 9.0 while in the pure $\text{E. coli}$ system the optimum is pH 8.0. The hybrid system is inhibited by NAD to the same extent as the pure $\text{E. coli}$ system.     

Studies on invitro DNA synthesis: II. Isolation of a protein which stimulates deoxynucleotide incorporation catalyzed by DNA polymerases of E.coli

Purified RNA polymerase, DNA polymerase III and unwinding protein of $\text{Escherichia}\text{coli}$ catalyze limited rifampicin sensitive fd or ØX 174 DNA-dependent DNA synthesis. A protein has been partially purified from $\text{E.}\text{coli}$ which stimulates rifampicin sensitive dXMP incorporation in this system 20 to 30 fold. This protein also stimulates DNA synthesis catalyzed by DNA polymerases I and II; the stimulation occurs in reactions primed with natural and synthetic DNAs as well as RNA-DNA hybrids. The protein is not a product of the known dna genes. In contrast to the above system of purified enzymes, rifampicin sensitive dXMP incorporation in crude extracts of $\text{E.}\text{coli}$ is specifically dependent on fd but not ØX 174 DNA. An additional factor has been isolated from extracts of $\text{E.}\text{coli}$ which restores specificity to the purified rifampicin sensitive system by preventing ØX 174 DNA from serving as a template.     

Identification and characterization of a new methylated amino acid in ribosomal protein L33 of Escherichiacoli

Methylated amino acids from ribosomal protein L33 of various $\text{Escherichia}\text{coli}$ strains (Q13, B and MRE600) were analyzed. It was found that while protein L33 from $\text{E.}\text{coli}$ Q13 contains two methylated neutral amino acids (peaks I and II), only one methylated neutral amino acid (peak I) was found in protein L33 derived from both $\text{E.}\text{coli}$ strains B and MRE600. The methylated amino acid present in peak I was identified as N-monomethylalanine by ion-exchange column chromatography, high-voltage paper electrophoresis and descending paper chromatography using different solvent systems. This marks the first time that N-monomethylalanine was found in any ribosomal protein.     

Influence of protease inhibitors and energy metabolism on intracellular protein breakdown in starving Escherichia coli

It has been reported that certain inhibitors of serine proteases block intracellular protein breakdown in $\text{E. coli}$ subjected to nutritional deprivation. We show here that the protease inhibitors p-toluene sulfonyl fluoride and pentamidine isethionate inhibit protein breakdown in $\text{E. coli}$ deprived of glucose, but not in bacteria starved for inorganic phosphate or ammonia. Furthermore, we find that the protease inhibitors cause a drastic decline in cellular ATP levels when glucose is omitted from the incubation medium. It is concluded that these protease inhibitors influence protein breakdown by interfering with cellular energy production, rather than by interacting with a specific serine protease.     

Ribosome specificity for the formation of guanosine polyphosphates

Ribosomes obtained from $\text{Bacillus brevis}$ (ATCC 8185) were slightly active in synthesizing guanosine polyphosphates, which activity was greatly stimulated by addition of $\text{Escherichia coli}$ stringent factor. $\text{Chlamydomonas reinhardtii}$ chloroplast ribosomes did not produce guanosine polyphosphates on incubation but responded with abundant synthesis to addition of the stringent factor from $\text{E. coli}$. In contrast, cytoplasmic ribosomes from the same organism did not respond. Interchange experiments between either subunit from chloroplasts with the $\text{E. coli}$ counterparts showed good activity. When the small subunit of cytoplasmic $\text{Chlamydomonas}$ ribosomes was combined with the large subunit of $\text{E. coli}$ or of chloroplasts, a small but definite response was obtained.     

Inhibition of mouse brain synaptosomal gamma-aminobutyric acid transport by pyridoxal 5'-phosphate

Crude lysates from a strain of enterotoxigenic $\text{E. coli}$ have been shown to catalyse the incorporation of [³²P] from [adenylate-³²P] NAD⁺ into an 11,000 dalton protein in rat liver membranes. [³²P] incorporation paralleled adenylate cyclase activation and the results suggest that the mechanism of action of the heat-labile $\text{E. coli}$ enterotoxin may involve ADP-ribosylation of an intracellular acceptor protein.     

Galactosyltransferase: confirmation of equilibrium-ordered mechanism.

A thermostable protein that strongly inhibits the soluble $\text{E. coli}$ D-alanine carboxypeptidase was isolated from a cell-free extract of $\text{E. coli B}$. The inhibitor was purified 140-fold by heat treatment, selective precipitation at pH 4.5, ion exchange chromatography on DEAE-cellulose and gel chromatography on Sephadex G-100. Inhibition of soluble D-alanine carboxypeptidase by this inhibitor is reversed by cations such as Mg⁺⁺ or Na⁺ and abolished by digestion of the inhibitor with proteolytic enzymes. The inhibitor does not affect either the particulate D-alanine carboxypeptidase of $\text{E. coli}$ or the growth of the bacteria.     

Synthesis of diphtheria toxin in E. coli cell-free lysate

An $\text{E. coli}$ cell-free lysate was used to translate $\text{C. diphtheriae}$ RNA from nontoxinogenic C₇(?), C₇ infected with β tox⁺ corynebacteriophage, and $\text{C. diphtheriae}$ strain PW8. De novo synthesis of toxin was detected by immune precipitation with antitoxin, ADP-ribosylation of mammalian elongation factor 2 and rabbit skin test. The results indicated that toxin is produced in the $\text{E. coli}$ protein synthesizing system primed with RNA from cells infected with tox⁺ bacteriophage and is absent in systems primed with RNA from C₇(?) cells.     

Esherichia coli pyruvate dehydrogenase complex: improved purification and the flavin content.

The $\text{E. coli}$ pyruvate dehydrogenase complex, when purified by published procedures, contains phosphotransacetylase and coenzyme A as trace contaminants as well as one or more spectral contaminants which interfere with spectral and radiochemical experiments. They can be removed by further chromatographic purification on columns of calcium phosphate gel-cellulose. The resulting complexes from $\text{E. coli}$ K12 or Crookes strain are indistinguishable with respect to visible spectrum, catalytic activity, and flavin content. The activity is the highest so far reported, 40–42 μmoles DPNH per min per mg of protein, and the flavin content is 1.8–2.4 nanomoles per mg of protein.     

On the primary structure of the Escherichia coli R4 cell wall lipopolysaccharide core.

From $\text{Escherichia coli}$ R4, and from some deeper rough mutants of it, the cell wall lipopolysaccharides were isolated and subjected to mild acid hydrolysis. By methylation/g.l.c./m.s. and other analyses of the core oligosaccharides thus obtained, the primary structure of the $\text{E. coli}$ R4 core (hexose and heptose region) was elucidated:

     

Peptide chain initiation with chemically formylated Met-tRNAs from E. coli and yeast

Chemically formylated Met-tRNA_m^Met and Met-tRNA_f^Met species from $\text{E.}$$\text{coli}$ and yeast were tested for their capacity to serve as chain-initiators in a cell-free system from $\text{E.}$$\text{coli}$. In the presence of R 17 mRNA, initiation factors and $\text{E.}$$\text{coli}$ ribosomes, all four Met-tRNAs could form functional initiation complexes as measured by ribosomal binding kinetics, fMet-puromycin formation and synthesis of a dipeptide fMet-Ala. Unformylated Met-tRNA_f^Met from $\text{E.}$$\text{coli}$ displayed significantly less activity as a peptide chain-initiator than the formylated Met-tRNA_m^Met species from $\text{E.}$$\text{coli}$ and yeast. Although the latter tRNAs were less effective initiators than the “physiological” initiator tRNAs, the data seem to indicate that a blocked α-amino group represents the major token of identification by which Met-tRNA is admitted to function in $\text{E.}$$\text{coli}$ peptide chain initiation.     

The effect of 5-azacytidine on E. coli DNA methylase.

5-Azacytidine, when added to growing $\text{E.}$$\text{coli}$ K12, causes a decrease in DNA methylation assayed $\text{in}$$\text{vitro}$. This decrease is greater when $\text{E.}$$\text{coli}$ DNA is used as substrate than when calf thymus DNA is used. The decrease in activity is not due to the inhibition of protein synthesis caused by this drug, since neither chloramphenicol nor rifampin causes a decrease in enzyme activity. The effect is specific for the DNA(cytosine-5)methylase; the methylation of adenine is not affected. The concentration of drug that inhibits the DNA methylase by 50% is the same concentration that inhibits cell growth by 50%.     

Responsibility of 16S RNA for the stimulation of polypeptide synthesis by spermidine.

From the studies on the spermidine stimulation of polyphenylalanine synthesis catalyzed by $\text{E. coli}$ 50S and reconstituted 30S particles containing 16S RNA and 30S ribosomal proteins from $\text{E. coli}$ and $\text{B. thuringiensis}$ in different kinds of combinations, it is concluded that 16S RNA is mainly responsible for the stimulation of polypeptide synthesis by spermidine.     

Localization of the lactose permease protein(s) in the E. coli envelope.

The amino acid double labeling technique was used to identify and localize membrane-bound lactose operon proteins in $\text{E.}\text{coli}$. Both the “M” protein, thought to be the $\text{y}$ gene product, and a polypeptide of MW ～15,000 appeared in the membrane following $\text{lac}$ operon induction. The amounts of these two proteins were approximately equal.The inner and outer membrane layers of the cell envelope were separated by sucrose density gradient centrifugation or by selective solubilization of inner membranes with the detergent Sarkosyl. When gentle lysis conditions were employed to prepare membrane vesicles, both $\text{lac}$ induced proteins fractionated with the inner membrane. However, the “M” protein was more easily randomized in the envelope structure by sonication than the 15,000 dalton component or an inner membrane marker enzyme.     

Preferential utilization of glutamine for amination of xanthosine 5'-phosphate to guanosine 5'-phosphate by purified enzymes from Escherichia coli

GMP synthetase was purified 180-fold from $\text{E. coli}$ B and 18-fold from the derepressed purine auxotroph, $\text{E. coli}$ B-96. The enzymes from both sources show the same preference for glutamine over ammonia as amino donor. Each is dimeric, consisting of subunits of molecular weight about 60,000. Thus the two are apparently identical. The similarities between GMP synthetase and xanthosine 5′-phosphate aminase of $\text{E. coli}$ B-96 (N. Sakamoto, G.W. Hatfield, and H.S. Moyed, J. Biol. Chem. (1972) $\text{247}$, 5880–5887) in respect to structure, state of derepression, and behavior during purification, lead us to the conclusion that the synthetase and the aminase are a single entity. We observe no loss or separation of glutamine-dependent activity upon purification of GMP synthetase and we suggest that such loss, reported by other workers, results artifactually by inactivation of an intrinsic glutamine-binding site. GMP synthetase appears not to contain a glutamine-binding subunit which is separable from the xanthosine 5′-phosphate-aminating component.     

Oxygen poisoning of NAD biosynthesis: a proposed site of cellular oxygen toxicity.

Quinolinate phosphoribosyl transferase was rapidly inactivated in $\text{Escherichia}\text{coli}$ exposed to hyperbaric oxygen. The enzyme is essential for de novo biosynthesis of NAD in $\text{E.}\text{coli}$ and man. Because of its sensitivity and essentiality, inactivation of this enzyme is proposed as a significant mechanism of cellular oxygen toxicity. Niacin which enters the NAD biosynthetic pathway below the oxygen-poisoned enzyme provided significant protection against the decrease in pyridine nucleotides and the growth inhibition from hyperoxia in $\text{E.}\text{coli}$ and could be useful in cases of human oxygen poisoning.     

Immunological properties of membrane fractions from wild type and dnaA mutants of Escherichia coli

Membrane vesicles from Escherichia coli wild type and an otherwise isogenic $\text{dna}\text{A}$ mutant were used to immunize rabbits. In addition, a membrane protein fraction, containing the material found deficient in $\text{dna}$A mutants, was purified by preparative polyacrylamide gel electrophoresis in sodium dodecylsulfate, and used for immunization. The antisera produced were analyzed by immunoelectrophoresis and immunofluorescence microscopy. The antisera obtained by immunization with membrane vesicles from either wild type or $\text{dna}\text{A}$ mutant membrane preparations were qualitatively similar in the precipitin bands seen after immunoelectrophoresis. The antisera obtained by immunization with the purified protein fraction contained a subset of the antibodies seen when whole vesicles were used for immunization. In a semiquantitative precipitin assay, the antisera prepared against whole membrane vesicles or the isolated protein fraction both caused the precipitation of more protein from sodium dodecylsulfate-solubilized membranes of wild type than of $\text{dna}\text{A}$ mutants. No difference was seen by immunoelectrophoresis between the protein composition of wild type or $\text{dna}\text{A}$ membrane preparations. Thus, the $\text{dna}\text{A}$ mutant appears to differ from the wild type in the quantitative composition of its membrane proteins, whereas no qualitative differences were detected.Fluorescein-conjugated antiserum preparations were employed to assess the reactivity of intact cells, spheroplasts and membrane vesicles with the antisera studied above. Wild type cells of E. coli have a barrier to reaction with the antisera; this barrier is removed when the cells are converted to spheroplasts or to membrane vesicle. Similarly, a highly permeable mutant of E. coli permits reaction of the antisera with unaltered cells. Antisera to both whole membrane vesicles and to the isolated protein fraction react identically with the cellular and subcellular preparations. Thus, antisera prepared from membrane proteins isolated after sodium dodecylsulfate-polyacrylamide gel electrophoresis can still recognize some antigens present in membrane vesicle preparations.