Isolation and characterization of a mutant of Escherichia coli blocked in the synthesis of putrescine

Biosynthesis of Arginine and Polyamines

Early investigations on arginine biosynthesis brought to light basic features of metabolic regulation. The most significant advances of the last 10 to 15 years concern the arginine repressor, its structure and mode of action in both E. coli and Salmonella typhimurium, the sequence analysis of all arg structural genes in E. coli and Salmonella typhimurium, the resulting evolutionary inferences, and the dual regulation of the carAB operon. This review provides an overall picture of the pathways, their interconnections, the regulatory circuits involved, and the resulting interferences between arginine and polyamine biosynthesis. Carbamoylphosphate is a precursor common to arginine and the pyrimidines. In both Escherichia coli and Salmonella enterica serovar Typhimurium, it is produced by a single synthetase, carbamoylphosphate synthetase (CPSase), with glutamine as the physiological amino group donor. This situation contrasts with the existence of separate enzymes specific for arginine and pyrimidine biosynthesis in Bacillus subtilis and fungi. Polyamine biosynthesis has been particularly well studied in E. coli, and the cognate genes have been identified in the Salmonella genome as well, including those involved in transport functions. The review summarizes what is known about the enzymes involved in the arginine pathway of E. coli and S. enterica serovar Typhimurium; homologous genes were identified in both organisms, except argF (encoding a supplementary OTCase), which is lacking in Salmonella. Several examples of putative enzyme recruitment (homologous enzymes performing analogous functions) are also presented.

Arginase in Leishmania

The presence of different sets of several enzymes that participate in the Krebs-Henseleit cycle has been used to identify several genera of trypanosomatids. One of these enzymes is arginase (L-arginine amidinohydrolase, E.C. 3.5.3.1), a metalloenzyme that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. Arginase activity has been detected in Leishmania, Crithidia and Leptomonas but not in Trypanosoma, Herpetomonas or Phytomonas. The ureotelic behavior of some trypanosomatids is not due to urea excretion but to the production of ornithine to supply the polyamine pathway, which is essential for replication. Leishmania is found inside macrophages in the mammalian host and to live in these cells, the parasite must escape from several microbicidal mechanisms, such as nitric oxide (NO) production mediated by inducible nitric oxide synthase (iNOS). Since arginase and iNOS use the L-arginine as substrate, the amount of this amino acid available for both pathways is critical for parasite replication. In both promastigotes and amastigotes, arginase is located in the glycosome indicating that arginine trafficking in the cell is used to provide the optimal concentration of substrate for arginase. Arginine uptake by the parasite is also important in supplying the arginase substrate. Leishmania responds to arginine starvation by increasing the amino acid uptake. In addition to the external supply, the internal L-arginine pool also governs the uptake of this amino acid, and the size of this internal pool is modulated by arginase activity. Thus, arginine uptake and arginase activity are important in establishing and maintaining Leishmania infection.

Filarial parasites possess an antizyme but lack a functional ornithine decarboxylase

In eukaryotes, the key player in polyamine metabolism is the ornithine decarboxylase (ODC) that catalyses the first and rate limiting step in cellular polyamine synthesis. The half life of ODC is strictly regulated by the antizyme (AZ), which promotes its degradation. Older reports on the polyamine situation in filarial parasites indicate a lack of ornithine decarboxylation activity and an increased uptake of polyamines. Our in silico analysis of the Brugia malayi genome revealed only an ODC-like protein that lacks essential residues. Consequently, the recombinant protein had no enzymatic ODC activity. Furthermore, only ODC-like genes were found in the available draft genomes of other filarial parasites. In this ODC-free scenario, we set out to investigate the AZ of O. volvulus (OvAZ). The expression of the recombinant protein allowed us to analyse the localization of OvAZ in different O. volvulus stages as well as to identify it as target for the human humoral immune response. Strong immunostaining was observed in the outer zone of the uterine epithelium as well as in the uterus lumen around the periphery of the developing parasite, indicating a potential role of the OvAZ in the control of polyamine levels during embryonic development. By employing a novel in vivo method using Caenorhabditis elegans, we postulate that the OvAZ enters the secretory pathway. Even though the ODCs are absent in filarial parasites, OvAZ has the ability to bind to various ODCs, thereby demonstrating the functionality of the conserved AZ-binding domains. Finally, pull-down assays show an interaction between B. malayi AZ and the B. malayi ODC-like protein, indicating that the B. malayi ODC-like protein might function as an AZI. Taken together, our results suggest that filarial species do not possess the ODC while retaining the ODC-regulatory proteins AZ and AZI. It is tempting to speculate that both proteins are retained for the regulation of polyamine transport systems.

Development of agmatine sensor using the combination of putrescine oxidase and agmatinase for squid freshness

Agmatine (Agm) is an indicator of squid freshness. The Agm sensor was developed using flow injection analysis (FIA) that consisted of the putrescine oxidase (PuOx) reactor, the agmatinase (AUH)-PuOx reactor and two oxygen electrodes. In the proposed sensor, the first step is that coexisting cadaverine (Cad) and putrescine (Put) are removed by passing through the PuOx reactor and the initial decomposition is determined by the amount of oxygen consumed, simultaneously. The second step is that the amount of Agm is determined by the amount of oxygen consumed in the AUH-PuOx reactor. The optimum conditions for the use of the Agm sensor were as follows: 50 mM HEPES containing MnSO4 at a final concentration of 5 mM, pH 8.0, flow rate of 0.6 mL min(-1) and injection volume of 50 microL. A single assay could be completed in approximately 3 min. A linear relationship was obtained between the output and the Agm concentration in the range of 0.01-1 mM Agm with a correlation coefficient of 0.999. The detection limit was 0.005 mM. The relative standard deviations (RSDs) were 3.14 and 1.19% (n = 20) for 0.1 and 0.3 mM Agm, respectively. The extracts of squid were injected into the proposed sensor and the results were compared with those obtained using the conventional high-performance liquid chromatography (HPLC) method. A correlation was observed between the results obtained by the proposed sensor and those obtained by the conventional method. The determination of squid freshness is one of the good uses of the proposed Agm sensor.

Poly amine Requirement for Streptomycin Action on Protein Synthesis in Bacteria

The effect of streptomycin on polypeptide synthesis in vivo and in vitro has been investigated using polyamine auxotrophic mutants of Escherichia coli grown in the presence or in the absence of putrescine. We found that streptomycin caused a marked inhibition of protein synthesis in polyamine-supplemented cells whereas bacteria starved for polyamines were less sensitive to the action of the antibiotic. Neomycin, kanamycin and kasugamycin had a behaviour similar to streptomycin while spectinomycin, gentamicin and tetracycline brought about a strong inhibition of protein synthesis both in polyamine-starved and unstarved bacteria. The increase of misreading induced by the addition of streptomycin in vivo was higher in extracts derived from bacteria cultivated in the presence of polyamines. This effect was observed in cell-free systems of streptomycin-sensitive and resistant strains. In contrast, spermidine added in vitro caused an improvement in the accuracy of translocation. Analysis of sodium dodecyl sulphate/polyacrylamide gel electrophoresis of the labelled polypeptides synthesized in vivo seems to indicate that the starvation for polyamine or the presence of streptomycin may lead to premature termination with the appearance of unfinished peptide chains.

Phylogeny of related functions: the case of polyamine biosynthetic enzymes

Genome annotation requires explicit identification of gene function. This task frequently uses protein sequence alignments with examples having a known function. Genetic drift, co-evolution of subunits in protein complexes and a variety of other constraints interfere with the relevance of alignments. Using a specific class of proteins, it is shown that a simple data analysis approach can help solve some of the problems posed. The origin of ureohydrolases has been explored by comparing sequence similarity trees, maximizing amino acid alignment conservation. The trees separate agmatinases from arginases but suggest the presence of unknown biases responsible for unexpected positions of some enzymes. Using factorial correspondence analysis, a distance tree between sequences was established, comparing regions with gaps in the alignments. The gap tree gives a consistent picture of functional kinship, perhaps reflecting some aspects of phylogeny, with a clear domain of enzymes encoding two types of ureohydrolases (agmatinases and arginases) and activities related to, but different from ureohydrolases. Several annotated genes appeared to correspond to a wrong assignment if the trees were significant. They were cloned and their products expressed and identified biochemically. This substantiated the validity of the gap tree. Its organization suggests a very ancient origin of ureohydrolases. Some enzymes of eukaryotic origin are spread throughout the arginase part of the trees: they might have been derived from the genes found in the early symbiotic bacteria that became the organelles. They were transferred to the nucleus when symbiotic genes had to escape Muller's ratchet. This work also shows that arginases and agmatinases share the same two manganese-ion-binding sites and exhibit only subtle differences that can be accounted for knowing the three-dimensional structure of arginases. In the absence of explicit biochemical data, extreme caution is needed when annotating genes having similarities to ureohydrolases.

In vitro construction of gshB::kan in Escherichia coli and use of gshB::kan in mapping the gshB locus

The Escherichia coli structural gene for glutathione synthetase, gshB, was cloned into pBR322. Plasmids containing gshB were able to complement the glutathione requirement of a trxA gshB double mutant, and cells containing the plasmids were found to have elevated levels of glutathione synthetase. A mutant gshB allele was constructed by inserting the kan gene from pUC4K into a unique HpaI site located within gshB. The resulting plasmid-encoded allele was used to replace a genomic gshB+ by homologous recombination. The resulting strain had no detectable glutathione synthetase activity. The gshB allele containing the kan insertion was used to map gshB on the E. coli chromosome by P1 transduction. The results indicated that gshB is located at 63.4 min, between metK and speC. The allele was further localized to a region of 3,100 to 3,120 kilobase pairs on the physical map (restriction map) of E. coli by DNA-DNA hybridization to a series of lambda bacteriophages (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987).

Activities and properties of putrescine-biosynthetic enzymes in Vibrio parahaemolyticus

The biosynthetic pathways for putrescine (Put) in Vibrio parahaemolyticus were delineated by measuring activities of the enzymes which would be involved in its biosynthesis. Experiments with labeled arginine and ornithine revealed that both of these amino acids were converted into Put by intact cells. The activities of three enzymes, arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and agmatine ureohydrolase (AUH), were detected in cell extracts. ADC and ODC of V. parahaemolyticus were similar in the following properties to the corresponding enzymes of Escherichia coli: 1) both decarboxylases showed a pH optimum at 8.25 and required pyridoxal phosphate and dithiothreitol for full activity; 2) while ODC was considerably activated by GTP, ADC was only slightly; 3) both decarboxylases were inhibited by polyamines; 4) ADC was inhibited by difluoromethylarginine, a potent inhibitor of bacterial ADC. However, in contrast to the corresponding enzymes of E. coli, the V. parahaemolyticus ADC showed no requirement for Mg2+, and the AUH was active over a wide pH range of 8.5-9.5 with a maximum at pH 9.0. Furthermore, in all 6 strains tested, the activity of ADC was obviously high compared with that of ODC, and AUH was present with a relatively high activity. Cultivation of these strains at a suboptimal NaCl concentration (0.5%) resulted in a pronounced increase in both ADC and AUH activities. These observations suggest that the important pathway for Put biosynthesis in V. parahaemolyticus is the decarboxylation of arginine by ADC and the subsequent hydrolysis of its product, agmatine, by AUH.

Formation of a compensatory polyamine by Escherichia coli polyamine-requiring mutants during growth in the absence of polyamines

The amounts of normal and compensatory polyamines of polyamine-requiring Escherichia coli mutants grown in the absence of polyamines were determined. Although aminopropylcadaverine, a compensatory polyamine, was synthesized by MA135 (speB) and DR112 (speA speB), no aminopropylcadaverine or only small amounts of aminopropylcadaverine were synthesized by EWH319 (speA speB speC speD) and MA261 (speB speC), respectively. The average mass doubling times of MA135, DR112, MA261, and EWH319 grown in the absence of polyamines were 113, 105, 260, and 318 min, respectively. The correlation of these values with the sum of spermidine plus aminopropylcadaverine suggested that aminopropylcadaverine is important for cell growth in the presence of limiting amounts of normal polyamines. This hypothesis is supported by the results of aminopropylcadaverine stimulation of the in vitro synthesis of polyphenylalanine and MS2 RNA replicase and of its stimulation of the growth of MA261. For the following reasons, it was concluded that aminopropylcadaverine was synthesized preferentially from cadaverine made by ornithine decarboxylase: aminopropylcadaverine was synthesized in relatively large amounts in cells (MA135 and DR112) which possess ornithine decarboxylase; ornithine decarboxylase catalyzed the decarboxylation of lysine in vitro, and the in vivo formation of aminopropylcadaverine was inhibited by an inhibitor of ornithine decarboxylase.

A probable new pathway for the biosynthesis of putrescine in Escherichia coli

Some cultures of Escherichia coli BGA8, a mutant unable to synthesize putrescine, showed a change of behaviour and could grow almost equally well in either the absence or the presence of polyamines after repeated periods of polyamine starvation. Experiments in vivo with radioactive precursors showed that the bacteria which evaded the polyamine requirement had recovered their ability to synthesize putrescine from glucose or glutamic acid, but not from ornithine or arginine. These results are in agreement with the fact that the polyamine-independent cells were still deficient in the enzymes ornithine decarboxylase and agmatinase. Our findings seem to indicate the existence of a new pathway synthesize putrescine which does not involve ornithine or arginine as intermediates.

Metabolic pathway for the utilization of L-arginine, L-ornithine, agmatine, and putrescine as nitrogen sources in Escherichia coli K-12

The pathway for the utilization of L-arginine, agmatine, L-ornithine, and putrescine as the sole nitrogen source by Escherichia coli K-12 has been elucidated. Mutants impaired in the utilization of one or more of the above compounds were isolated, and their growth on the different compounds as a sole source of nitrogen and the activities of enzymes of the putative pathway were examined. Our results show that L-arginine is first decarboxylated to agmatine, which is hydrolyzed to urea and putrescine. L-Ornithine is decarboxylated to putrescine. Putrescine is transaminated to gamma-aminobutyraldehyde, which is oxidized to gamma-aminobutyric acid. gamma-Aminobutyric acid is degraded to succinate. The gene for putrescine aminotransferase was located at 89 min on the E. coli K-12 chromosome, and the gene for gamma-aminobutyraldehyde (pyrroline) dehydrogenase was mapped at approximately 30 min.

Ornithine decarboxylase as target of chemotherapy

Ornithine decarboxylase is a key enzyme in polyamine synthesis and growth of mammalian cells. In this chapter I review recent reports on the purification and properties of the pure enzyme, and on the localization, synthesis and regulation of the enzyme in the cell. The use of monospecific antibodies, radiolabeled irreversible inhibitors and cDNA clones for studying enzyme localization, turnover and regulation, is briefly described. This first part is meant to serve as a basis for the analysis of ornithine decarboxylase as a target of chemotherapy. A selection of the most potent inhibitors of ornithine decarboxylase is presented and the effects of some of these in cell culture, in animals and in the clinical setting are reviewed.

Regulation of growth and macromolecular synthesis by putrescine and spermidine in Pseudomonas aeruginosa

Growth of P. aeruginosa, slowed by the addition of monofluoromethylornithine, difluoromethylarginine and dicyclohexylammonium sulfate, could be restored by addition of 0.1 mM putrescine plus 0.1 muM spermidine, or 0.1 mM spermidine or 5 mM putrescine by themselves. Lower concentrations of putrescine (0.1 mM - 1 mM) also partially reversed the growth inhibition. Conversion of putrescine to spermidine continued, although at a markedly reduced ratio, in the drug-inhibited cells, but intracellular spermidine concentrations remained depressed suggesting that reversal of inhibition by putrescine may be a direct effect. There was appreciable back-conversion of any added spermidine to putrescine with a demonstrable increase in total intracellular putrescine levels, making conclusions on the effects of spermidine ambiguous. Spermine (0.1 mM), a polyamine not present in bacteria, was also effective in reversing growth inhibition, probably because of its conversion into spermidine and putrescine. The effects of putrescine, spermidine and spermine were specific in that the non-physiological amines, 1,3-diaminopropane, 1,5-diaminopentane (cadaverine), 1,6-diaminohexane, or 1,7-diaminoheptane could not reverse the effects of the three drugs. Rates of total protein, RNA and DNA synthesis were all slowed to the same extent as growth rate and showed similar recovery with the addition of putrescine or spermidine. A role for putrescine in P. aeruginosa growth processes is suggested.

Putrescine and spermidine sensitivity of lysine decarboxylase in Escherichia coli: evidence for a constitutive enzyme and its mode of regulation

Cells of Escherichia coli grown under physiological (noninducing) conditions have a low level of lysine decarboxylase activity. This activity differs from the enzyme found in induced cells in its sensitivity to putrescine (33% of control in the presence of 20 mM putrescine). It is also sensitive to spermidine (20% of control in the presence of 6 mM spermidine). A mixture of putrescine and spermidine completely eliminated lysine decarboxylase activity. This provides evidence for the existence of a biosynthetic enzyme and suggests a mechanism to explain the appearance of cadaverine in polyamine-depleted cells.

Spermidine requirement for cell proliferation in eukaryotic cells: structural specificity and quantitation

Six structural homologs of spermidine and five of its precursor, putrescine, were studied for their ability to prevent cytostasis of cultured L1210 leukemia cells induced by alpha-difluoromethylornithine (DFMO), a specific inhibitor of putrescine biosynthesis. High-performance liquid chromatography and competition studies with spermidine indicated that the homologs, which vary in the length of the carbon chain separating the amines, penetrated the cells. The structural specificity of the spermidine carrier was defined. Three of the six spermidine homologs supported cell growth during a 48-hour incubation in the presence of DFMO, indicating that a two-carbon extension of spermidine structure was tolerated for biological function. Two of the five putrescine homologs supported growth after being converted by the cells to their respective spermidine homologs. The central nitrogen of spermidine appears to be essential for function since diamines of chain length comparable to that of spermidine did not prevent DFMO cytostasis. No more than 15 percent of the spermidine normally present in L1210 cells was required for cell proliferation in the presence of DFMO.

Induction of choline transport and its role in the stimulation of the incorporation of choline into phosphatidylcholine by polyamines in a polyamine auxotroph of Saccharomyces cerevisiae

1. A mutant of Saccharomyces cerevisiae, defective in ornithine decarboxylase, was isolated. A prolonged culture of the mutant in a polyamine-free medium resulted in a great decrease in the polyamine content and in cessation of growth. The addition of polyamines to the culture induced the growth after a lag period of 5--6.5 h. The growth rate in the presence of polyamine was comparable to that of the wild-type strain. The effectiveness of polyamines was as follows: spermidine greater than putrescine approximately equal to spermine. 2. Phosphatidylcholine-synthesizing activity during the lag phase of growth was determined by measuring the rate of incorporation of [14C]choline into phosphatidylcholine. The incorporation rate was markedly increased with time by polyamine prior to the initiation of cell division. Polyamines were effective in the following order: spermidine greater than putrescine approximately equal to spermine. Experiments with methylglyoxal bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase, showed that putrescine stimulates cell growth and choline incorporation into phosphatidylcholine after it has been converted into spermidine in the cell. 3. The induction of the choline transport system was shown to be responsible for the increase in the rate of incorporation of [14C]choline into phosphatidylcholine effected by polyamines. A low concentration of cycloheximide completely prevented the induction of choline transport by polyamines. The levels of the CDP-choline pathway enzymes such as choline kinase, cholinephosphate cytidyltransferase and cholinephosphotransferase were not significantly changed.

Speed-accuracy relationships during in vitro and in vivo protein biosynthesis

Poly U-directed incorporation of phenylalanine and leucine into polypeptide has been described in at least 50 papers since 1961. In general, high translation activities are associated with high accuracies, and vice-versa. Moreover, a vast body of independent experimental data (effect of ethanol, temperature, urea, aminoglycosides, etc... on protein synthesis) put together here suggests that, in many circumstances, speed and accuracy of elongation are correlated. This result is to be contrasted with the view that the speed and the fidelity of protein synthesis are two opposing parameters. In this report, recent experimental data on the nature and effect of ribosomal ambiguity (ram) and streptomycin resistance (Strr) mutations are reexamined. Models on the action of streptomycin and other misreading-inducing antibiotics, as well as long-standing ideas on the control of misreading in mammalian systems are critically evaluated. An explanation is provided for the long-befuddling data on the action of gentamicin.

Structural specificity of the spermidine requirement of an Escherichia coli auxotroph

A homologous series of spermidine analogs was synthesized with the general structure NH3+ (CH2)nNH2+(CH2)3NH3+, where spermidine has n = 4. The influence of these compounds on growth and on the syntheses of protein and messenger ribonucleic acid was examined in a spermidine auxotroph of Escherichia coli. All of the homologs tested were taken up by the cells to an intracellular level equivalent to the level of spermidine which gives optimal growth. With increasing chain length of the homologs, there was reduced ability to stimulate growth. The homologs with n = 7 and n = 8 were essentially inactive. A similar specificity was observed when the ability of the homologs to restore the rates of protein and messenger ribonucleic acid chain elongation was compared to that of spermidine. These results suggest that a definite spatial arrangement of the amino groups of spermidine is required for productive interaction at its intracellular site(s) of action.

Metabolic products of microorganisms 167. Cyclopaldic acid from Aspergillus duricaulis. 1. Production, isolation and bioloical properties

In the course of a screening for new metabolites from fungi we isolated a substance with antimicrobial activity from cultures of Aspergillus duricaulis (CBS 481.65) (Tü 679). It was antagonized by putrescine, spermidine, spermine, arginine, citrulline, lysine, ornithine, in higher concentration by aspraagine and glutamine too. The effect of ethylenediaminetetraacetate on the susceptibility of Streptomyces viridochromogenes (Tü 57) and Bacillus subtilis ATCC 6051 to this antibiotic has been studied. The substance was characterized and identified as cyclopaldic acid.

Polyamines and protein synthesis: studies in various polyamine-requiring mutants of Escherichia coli

Different Escherichia coli mutants auxotrophic for polyamines were studied in order to investigate the relationships among polypeptide synthesis in cell-free systems, ribosomal distribution profiles and endogenous polyamine pools. The in vitro protein synthetic activity and the polyribosomal content were reduced in extracts from putrescine-starved cells of the double mutans MA 255 and MA 261, but not in the arginine-conditional auxotroph DK 6. Putrescine addition to the cultures of all these strains previously starved for polyamines, provoked a shift towards monomers in the equilibrium involving ribosomal particles. Concomitant changes in the intracellular levels of polyamines were observed: putrescine and spermidine increased markedly, and cadaverine disappeared.

Properties of an Escherichia coli K-12 mutant defective in the transport of arginine and ornithine

A canavanine-resistant mutant strain, defective in the transport of arginine and ornithine, was isolated and characterized. Experiments presented show that both the kinetics of influx and the steady state of accumulation of arginine and ornithine are affected by the mutation, whereas the activity of other related transport systems remains unchanged. On the basis of competitive studies, it is concluded that L-canavanine can inhibit efficiently the arginine-specific uptake system. D-Arginine appears to be a moderate inhibitor. None of the basic amino acid-binding proteins of the mutant strain showed detectable alterations in terms of quantity, physical properties, or affinity constants. Studies on the relationship between the number of transport carriers and the steady state of accumulation of arginine suggested the presence of a reduced number of membrane carriers in the mutant strain. It is proposed that the mutation affects a regulatory gene concerned with controlling the amount of membrane carriers produced, which are components of the arginine- and ornithine-specific uptake systems. The mutation maps at min 62 on the recalibrated linkage map of Escherichia coli K-12, in a locus closely linked or identical to argP.

Alpha-methyl ornithine, a potent competitive inhibitor of ornithine decarboxylase, blocks proliferation of rat hepatoma cells in culture

A biphasic increase of putrescine concentration occurs in rat hepatoma tissue culture cells induced to proliferate. DL-alpha-Methyl ornithine, a competitive inhibitor of ornithine decarboxylase ( L-ornithine carboxylyase, EC 4.1.1.7) of hepatoma tissue culture cells, blocks the usual increases of putrescine and spermidine concentrations in these cells, and causes a rapid fall in the levels of putrescine which is followed by a striking decrease of spermidine. In parallel with the depletion of these amines, incorporation of [3H]thymidine into DNA and cell proliferation are inhibited. Addition of putrescine, spermidine, or spermine results in an immediate resumption of cell proliferation. Cell proliferation is also restored by L-ornithine presumably due to in situ competitive inhibition of ornithine decarboxylase. These findings of hepatoma tissue culture cells support the concept that polyamines play an essential function in the cell division processes.

Arginine decarboxylase from a Pseudomonas species

An arginine decarboxylase has been isolated from a Pseudomonas species. The enzyme is constitutive and did not appear to be repressed by a variety of carbon sources. After an approximately 40-fold purification, the enzyme appeared more similar in its properties to the Escherichia coli biosynthetic arginine decarboxylase than to the E. coli inducible (biodegradative) enzyme. The Pseudomonas arginine decarboxylase exhibited a pH optimum of 8.1 and an absolute requirement of Mg2+ and pyridoxal phosphate, and was inhibited significantly at lower Mg2+ concentrations by the polyamines putrescine, spermidine, and cadaverine. The Km for L-arginine was about 0.25 mM at pH 8.1 AND 7.2. The enzyme was completely inhibited by p-chloromercuribenzoate. The inhibition was prevented by dithiothreitol, a feature that suggests the involvement of an -SH group. Of a variety of labeled amino acids tested, only L-arginine, but not D-arginine was decarboxylated. D-Arginine was a potent inhibitor of arginine decarboxylase with a Ki of 3.2 muM.

Chemically defined media for growing anaerobic bacteria of the genus Veillonella

A chemically defined medium for Veillonella parvula and V. alcalescens is described. Some nutritional aspects of the two strains used were examined: the optimum concentration of reducing agents, the requirements for amino acids, diamines, vitamins and other growth factors, and the conditions needed for well balanced nutrition. No specific requirements for single amino acids were observed. A combination of L-cysteine, DL-aspartic acid, L-glutamic acid, L-serine and L-tyrosine, promoted growth. In V. alcalescens, serine could substitute both arginine and tryptophan (or histidine). No growth was obtained with ammonium salts as the sole N source. Decarboxylation of L-ornithine, L-lysine and L-arginine was not demonstrated in the Veillonella parvula strain, which required putrescine or cadaverine for growth. Spermine, spermidine, L-lysine, L-ornithine and L-arginine, could not substitute putrescine in Veillonella parvula. Veillonella alcalescens, which does not require putrescine in the medium, was able to decarboxylate L-ornithine while forming putrescine.

Ribosomal distribution in a polyamine auxotroph of Escherichia coli

The distribution of ribosomal particles has been studied in a polyamine-deficient mutant of Escherichia coli by sucrose gradient centrifugation analysis. Lysates from starved cells contained less 70S monomers and 30S subunits but more 50S particles than those prepared from bacteria supplemented with putrescine. The addition of the polyamine to putrescine-depleted cells induced a rapid change of the ribosomal profile. A similar effect could be obtained in vitro by equilibrium dialysis against a polyamine-containing solution. The ribosomal pattern obtained from starved bacteria was specific for polyamine deficiency. We conclude that the changes in ribosomal profiles upon restoration of putrescine levels in previously starved cells denote a shift of the equilibrium between 30S-50S couples and ribosomal subunits.

Characterization of a naturally occurring diamine auxotroph of Veillonella alcalescens

Veillonella alcalescens strain ATCC 17745 was shown to require putrescine or cadaverine for growth. None of the other compounds tried, including magnesium and spermidine, were able to substitute for the diamines. Studies with labeled diamines showed that spermidine was made from putrescine in this organism. A polyamine analogous to spermidine, but made from cadaverine, was not found. A combination of growth experiments and chemical assays suggested that protein synthesis was limited in diamine-starved cells. Protein synthesis occurred prior to nucleic acid synthesis when putrescine was added to starved cells.

Isolation, characterization, and mapping of Escherichia coli mutants blocked in the synthesis of ornithine decarboxylase

Several Escherichia coli K-12 mutants blocked in the synthesis of ornithine decarboxylase (OD) were isolated after transduction for serA+ in a strain (MA197) blocked in agmatine ureohydrolase (AUH) with a mutagenized phage lysate of P1. The new double-polyamine mutants were characterized by an unconditional polyamine dependence; either putrescine or spermidine was required for normal growth. The mutational block was varified by the demonstration of a virtual absence of OD activity in cellular extracts. The mutation, designated speC, was mapped by P1 transduction in several strains and was shown to have a cotransduction frequency of 17.2% with serA. Map order was established as serA speB speC metK. A derivative of one of the OD mutants having wild-type levels of AUH and blocked in OD was utilized along with an OD AUH mutant and an OD+ AUH strain to explore the phenomenon of "pathway selection" using growth rate as a parameter. Polyamine pool studies were carried out simultaneously. The results presented here support the hypothesis of pathway selection, implying a preferential utilization of exogenous arginine rather than endogenously produced arginine in polyamine biosynthesis.

Polyamine limitation of growth slows the rate of polypeptide chain elongation in Escherichia coli

The rate of polypeptide chain elongation during steady-state, polyamine-limited growth of a mutant of Escherichia coli was measured by two independent techniques. Analysis of polysome patterns gave values of 17.5 and 9.5 amino acids per s at 37 C in unstarved and polyamine-limited cells, respectively. From the kinetics of entry of labeled amino acids into polypeptides of defined molecular weights, values at 30 C of 10.1 and 5.8 amino acids per s were obtained for unstarved and polyamine-limited cultures, respectively. Correction of these values to 37 C resulted in rates of 15.0 and 8.7 amino acids per s. These results support the previous conclusion, based on the kinetics of beta-galactosidase induction, that polyamine starvation decreases the rate of protein synthesis by limiting the velocity of polypeptide chain elongation.

Control of cell division in bacteria

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Growth of ribonucleic acid bacteriophage f2 in a conditional putrescine auxotroph of Escherichia coli: evidence for a polyamine role in translation

The ribonucleic acid (RNA) bacteriophage, f2, grows poorly in a conditional putrescine auxotroph during polyamine starvation. The addition of putrescine simultaneously with f2 enhances phage growth, shortens the latent period, and increases the burst size. The stimulation of f2 growth is reflected in higher rates of phage RNA and protein syntheses as measured by radioactive labeling of infected cells in the presence of rifampin. Putrescine does not affect f2 adsorption or the penetration of its RNA. Rather, in vitro assays demonstrate that in putrescine-supplemented cells more molecules of f2 replicase are made per incoming parental RNA than in polyamine-starved cultures. The ability of polyamines to stimulate the translation of a preformed messenger suggests a physiological role for these organic cations in normal protein synthesis.

Phospholipid turnover in a conditional polyamine auxotroph of Escherichia coli

Polyamines are required for rapid phospholipid turnover in Escherichia coli growing in media of low osmolarity.

Polyamine synthesis and accumulation in Escherichia coli infected with bacteriophage R17

We have studied the biosynthesis of polyamines during the multiplication of the RNA bacteriophage R17. R17-sensitive strains of Escherichia coli were derived from the stringent CP78 and the relaxed mutant derivative CP79. The cells were infected with R17 in the presence or absence of arginine, a required amino acid, and both the RNA and polyamine contents of the bacteria were determined before and after the infection. The uninfected CP79 rel derivative accumulated RNA and spermidine in the absence of arginine, unlike the stringent organism that accumulated neither under these conditions. After R17 infection, the stringent strain accumulated RNA and spermidine in the presence or absence of arginine. The data indicate a close correlation between the synthesis of RNA and spermidine, suggesting a significant role for this polyamine in the multiplication of phage R17.

Influence of polyamine limitation on the chain growth rates of beta-galactosidase and of its messenger ribonucleic acid

The rates of elongation of beta-galactosidase and its messenger ribonucleic acid (RNA) were estimated in a polyamine-deficient mutant of Escherichia coli through an analysis of the kinetics of enzyme induction. The chain growth of beta-galactosidase was calculated from the time required after the appearance of an amino terminal fragment of 60 amino acids (auto-alpha) until completed enzyme began to accumulate. The elongation rate of beta-galactosidase messenger RNA was estimated from the time after induction at which streptolydigen-resistant, enzyme-forming capacity first appeared. Upon polyamine starvation, the rate of polypeptide elongation slowed from 17 to 10 amino acids per s and the messenger RNA elongation rate decreased from 47 to 30 nucleotides per s. These reductions in polymerization rates were proportional to the decrease in cellular growth rate produced by polyamine starvation. It was concluded that, although it is quite unlikely that polyamine levels are involved in regulation of cell growth, they may be acting as cofactors in the synthesis of RNA or protein, or both.

Mutant of Escherichia coli K-12 defective in the transport of basic amino acids

Escherichia coli K-12 possesses two active transport systems for arginine, two for ornithine, and two for lysine. In each case there is a low- and a high-affinity transport system. They have been characterized kinetically and by response to competitive inhibition by arginine, lysine, ornithine and other structurally related amino acids. Competitors inhibit the high-affinity systems of the three amino acids, whereas the low-affinity systems are not inhibited. On the basis of kinetic evidence and competition studies, it is concluded that there is a common high-affinity transport system for arginine, ornithine, and lysine, and three low-affinity specific ones. Repression studies have shown that arginine and ornithine repress each other's specific transport systems in addition to the repression of their own specific systems, whereas lysine represses its own specific transport system. The common transport system was found to be repressible only by lysine. A mutant was studied in which the uptake of arginine, ornithine, and lysine is reduced. The mutation was found to affect both the common and the specific transport systems.

Stable ribonucleic acid synthesis in stringent (rel+) and relaxed (rel-) polyamine auxotrophs of Escherichia coli K-12

The relationship of polyamines to stable ribonucleic acid (RNA) synthesis under conditions of amino acid withdrawal or chloramphenicol treatment was examined with the use of a closely related rel(+), rel(-) pair conditionally incapable of synthesizing putrescine. Under conditions of polyamine starvation, the cellular sperimidine level fell to one-third to one-half of the value observed in putrescine-supplemented cultures and putrescine became undetectable; cadaverine was synthesized by both strains, but the relaxed strain, MA 252, accumulated less cadaverine per cell than its stringent twin, MA 254. Upon amino acid withdrawal, the stringent strain remained stringent whether starved of or supplemented with polyamines. Similarly, the relaxed strain was capable of making RNA either with or without polyamine starvation. On the addition of chloramphenicol or upon amino acid withdrawal in the relaxed strain, supplementation with spermidine had no effect on the initial rate of RNA synthesis, although RNA accumulation was greater in the presence of added spermidine. Spermidine added at the conclusion of RNA synthesis prompted additional synthesis, although preincubation with spermidine again had no effect on the initial rate. All forms of stable RNA species were made with polyamine supplementation. The present data appear to rule out the possibility that polyamines are primary causative agents in stimulating RNA synthesis, but rather suggest an indirect or secondary role for spermidine in which the polyamines "stimulate" stable RNA synthesis probably by relieving RNA product inhibition of RNA synthesis.