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Jakočiūnė D, Herrero-Fresno A, Jelsbak L, Olsen JE. Highly expressed amino acid biosynthesis genes revealed by global gene expression analysis of Salmonella enterica serovar Enteritidis during growth in whole egg are not essential for this growth. Int J Food Microbiol 2016; 224:40-6. [DOI: 10.1016/j.ijfoodmicro.2016.02.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 02/12/2016] [Accepted: 02/21/2016] [Indexed: 01/17/2023]
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Griffin J, Engel PC. An Examination by Site-Directed Mutagenesis of Putative Key Residues in the Determination of Coenzyme Specificity in Clostridial NAD-Dependent Glutamate Dehydrogenase. Enzyme Res 2011; 2011:595793. [PMID: 21876794 PMCID: PMC3157743 DOI: 10.4061/2011/595793] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 04/28/2011] [Accepted: 05/04/2011] [Indexed: 12/04/2022] Open
Abstract
Sequence and structure comparisons of various glutamate dehydrogenases (GDH) and other nicotinamide nucleotide-dependent dehydrogenases have potentially implicated certain residues in coenzyme binding and discrimination. We have mutated key residues in Clostridium symbiosum NAD+-specific GDH to investigate their contribution to specificity and to enhance acceptance of NADPH. Comparisons with E. coli NADPH-dependent GDH prompted design of mutants F238S, P262S, and F238S/P262S, which were purified and assessed at pH 6.0, 7.0, and 8.0. They showed markedly increased catalytic efficiency with NADPH, especially at pH 8.0 (∼170-fold for P262S and F238S/P262S with relatively small changes for NADH). A positive charge introduced through the D263K mutation also greatly increased catalytic efficiency with NADPH (over 100-fold at pH 8) and slightly decreased activity with NADH. At position 242, “P6” of the “core fingerprint,” where NAD+- and NADP+-dependent enzymes normally have Gly or Ala, respectively, clostridial GDH already has Ala. Replacement with Gly produced negligible shift in coenzyme specificity.
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Affiliation(s)
- Joanna Griffin
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
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Santos M, Rebordinos L, Gutiérrez S, Cardoza RE, Martín JF, Cantoral JM. Characterization of the gdhA gene from the phytopathogen Botrytis cinerea. Fungal Genet Biol 2001; 34:193-206. [PMID: 11728157 DOI: 10.1006/fgbi.2001.1298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A 3.48-kb DNA region containing the gdhA gene, which codifies the NADP-dependent glutamate dehydrogenase enzyme from Botrytis cinerea, has been cloned and characterized. A fragment of 2351 nucleotides was sequenced and found to contain an ORF of 1350 bp that encodes a protein of 450 amino acids. The gene, containing two introns that showed polymorphic size between them, was located by pulsed-field gel electrophoresis in chromosome X in seven strains, which were isolated from several hosts and had different levels of pathogenesis. The protein was similar to the gdhA of various other organisms, with nine highly conserved motifs that included the known active site sequence. The cloned gene was proven to be functional since it complemented two different Aspergillus nidulans gdhA mutants, restoring high levels of NADP-dependent glutamate dehydrogenase activity to the transformants. gdhA was transcribed as a monocistronic transcript of 1.7 kb starting at an A or a T, located 40 or 47 bp, respectively, upstream from the initial ATG codon of the ORF. Transcription levels of the gdhA gene were high during the rapid growth phase. Very high expression levels of the gdhA gene were observed in media with asparagine as the nitrogen source, whereas glutamic acid repressed transcription of the gdhA gene. Similarly high levels of gdhA gene transcription were observed in media with acetate as the carbon source, while glycerol strongly repressed gdhA gene transcription. These results indicate that expression of the gdhA gene is subject to strong nitrogen and carbon regulation at the transcriptional level.
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Affiliation(s)
- M Santos
- Laboratorio de Microbiología y Genética, Facultad de Ciencias del Mar y Ambientales, Puerto Real (Cádiz), E11510, Spain
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4
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Hu P, Leighton T, Ishkhanova G, Kustu S. Sensing of nitrogen limitation by Bacillus subtilis: comparison to enteric bacteria. J Bacteriol 1999; 181:5042-50. [PMID: 10438777 PMCID: PMC93994 DOI: 10.1128/jb.181.16.5042-5050.1999] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/1999] [Accepted: 06/11/1999] [Indexed: 11/20/2022] Open
Abstract
Previous studies showed that Salmonella typhimurium apparently senses external nitrogen limitation as a decrease in the concentration of the internal glutamine pool. To determine whether the inverse relationship observed between doubling time and the glutamine pool size in enteric bacteria was also seen in phylogenetically distant organisms, we studied this correlation in Bacillus subtilis, a gram-positive, sporulating bacterium. We measured the sizes of the glutamine and glutamate pools for cells grown in batch culture on different nitrogen sources that yielded a range of doubling times, for cells grown in ammonia-limited continuous culture, and for mutant strains (glnA) in which the catalytic activity of glutamine synthetase was lowered. Although the glutamine pool size of B. subtilis clearly decreased under certain conditions of nitrogen limitation, particularly in continuous culture, the inverse relationship seen between glutamine pool size and doubling time in enteric bacteria was far less obvious in B. subtilis. To rule out the possibility that differences were due to the fact that B. subtilis has only a single pathway for ammonia assimilation, we disrupted the gene (gdh) that encodes the biosynthetic glutamate dehydrogenase in Salmonella. Studies of the S. typhimurium gdh strain in ammonia-limited continuous culture and of gdh glnA double-mutant strains indicated that decreases in the glutamine pool remained profound in strains with a single pathway for ammonia assimilation. Simple working hypotheses to account for the results with B. subtilis are that this organism refills an initially low glutamine pool by diminishing the utilization of glutamine for biosynthetic reactions and/or replenishes the pool by means of macromolecular degradation.
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Affiliation(s)
- P Hu
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
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Botsford JL, Alvarez M, Hernandez R, Nichols R. Accumulation of glutamate by Salmonella typhimurium in response to osmotic stress. Appl Environ Microbiol 1994; 60:2568-74. [PMID: 7915510 PMCID: PMC201685 DOI: 10.1128/aem.60.7.2568-2574.1994] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Salmonella typhimurium accumulates glutamate in response to osmotic stress. Cells in aerobic exponential growth have an intracellular pool of approximately 125 nmol of glutamate mg of protein-1. When cells were grown in minimal medium with 500 mM NaCl, KCl, or sucrose, 290 to 430 nmol of glutamate was found to accumulate. Values were lower when cells were harvested in stationary phase. Cells were grown in conventional medium, harvested, washed, resuspended in the control medium or in medium with osmolytes, and aerated for 1 h. With aeration, glutamate was found to accumulate at levels comparable to those observed in exponential cultures. Antibiotics inhibiting protein synthesis did not affect glutamate accumulation when cells were aerated. Strains with mutations in glutamate synthase (glt) or in glutamate dehydrogenase (gdh) accumulated nearly normal levels of glutamate under these conditions. A double (gdh glt) mutant accumulated much less glutamate (63.9 nmol mg of protein-1), but a 1.9-fold excess accumulated when cells were aerated with osmotic stress. Methionine sulfone, an inhibitor of glutamate synthase, did not prevent accumulation of glutamate in cells aerated with osmotic stress. Glutamate dehydrogenase is thought to have minimum activity when ammonium is limiting. Resuspending cells with limiting ammonium reduced glutamate production but did not eliminate accumulation of excess glutamate when cells were osmotically stressed. Amino oxyacetic acid, an inhibitor of transamination reactions, did not prevent accumulation of excess glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J L Botsford
- Department of Biology, New Mexico State University, Las Cruces 88003
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Haeffner-Gormley L, Chen Z, Zalkin H, Colman RF. Importance of lysine-286 at the NADP site of glutamate dehydrogenase from Salmonella typhimurium. Biochemistry 1992; 31:7807-14. [PMID: 1510967 DOI: 10.1021/bi00149a010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Affinity labeling studies of NADP(+)-glutamate dehydrogenase from Salmonella typhimurium have shown that the peptide Leu-282-Lys-286 is located near the coenzyme site [Haeffner-Gormley et al. (1991) J. Biol. Chem. 266, 5388-5394]. The present study was undertaken to evaluate the role of lysine-286. The mutant enzymes K286R, K286Q, and K286E were prepared by site-directed mutagenesis, expressed in Escherichia coli, and purified. The Vmax values (micromoles of NADPH per minute per milligram of protein) were similar for WT (270), K286R (529), K296Q (409), and K286E (382) enzymes. As measured at pH 7.9, the Km value for NADPH was much greater for K286E (280 microM) than for WT (9.8 microM), K286R (30 microM), or K286Q (66 microM) enzymes. The efficiencies (kcat/Km) of the WT and K286R mutant were similar (1.2 x 10(3) min-1 microM-1 and 1.0 x 10(3) min-1 microM-1, respectively) while those of K286Q (0.30 x 10(3) min-1 microM-1) and K286E (0.07 x 10(3) min-1 microM-1) were greatly reduced. The decreased efficiency of the K286E mutant results from the increase in Km-NADPH, consistent with a role for a basic residue at position 286 which enhances the binding of NADPH. Plots of Vmax vs pH showed the pH optima to be 8.1-8.3 for all enzymes at saturating NADPH concentrations. A 40-fold increase in Km-NADPH for K286E was observed as the pH increased from 5.98 to 8.08, from which a unique pKe of 6.5 was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Haeffner-Gormley
- Department of Chemistry and Biochemistry, University of Delaware, Newark 19716
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Teller JK, Smith RJ, McPherson MJ, Engel PC, Guest JR. The glutamate dehydrogenase gene of Clostridium symbiosum. Cloning by polymerase chain reaction, sequence analysis and over-expression in Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 206:151-9. [PMID: 1587267 DOI: 10.1111/j.1432-1033.1992.tb16912.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The gene encoding the NAD(+)-dependent glutamate dehydrogenase (GDH) of Clostridium symbiosum was cloned using the polymerase chain reaction (PCR) because it could not be recovered by standard techniques. The nucleotide sequence of the gdh gene was determined and it was overexpressed from the controllable tac promoter in Escherichia coli so that active clostridial GDH represented 20% of total cell protein. The recombinant plasmid complemented the nutritional lesion of an E. coli glutamate auxotroph. There was a marked difference between the nucleotide compositions of the coding region (G + C = 52%) and the flanking sequences (G + C = 30% and 37%). The structural gene encoded a polypeptide of 450 amino acid residues and relative molecular mass (M(r) 49,295 which corresponds to a single subunit of the hexameric enzyme. The DNA-derived amino acid sequence was consistent with a partial sequence from tryptic and cyanogen bromide peptides of the clostridial enzyme. The N-terminal amino acid sequence matched that of the purified protein, indicating that the initiating methionine is removed post-translationally, as in the natural host. The amino acid sequence is similar to those of other bacterial GDHs although it has a Gly-Xaa-Gly-Xaa-Xaa-Ala motif in the NAD(+)-binding domain, which is more typical of the NADP(+)-dependent enzymes. The sequence data now permit a detailed interpretation of the X-ray crystallographic structure of the enzyme and the cloning and expression of the clostridial gene will facilitate site-directed mutagenesis.
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Affiliation(s)
- J K Teller
- Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, England
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Haeffner-Gormley L, Chen ZD, Zalkin H, Colman RF. Reaction of the nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]adenosine 2',5'-bisphosphate at the coenzyme site of wild-type and mutant NADP(+)-specific glutamate dehydrogenases from Salmonella typhimurium. Arch Biochem Biophys 1992; 292:179-89. [PMID: 1309291 DOI: 10.1016/0003-9861(92)90066-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Wild-type glutamate dehydrogenase (EC 1.4.1.4) from Salmonella typhimurium reacts at 25 degrees C in 0.1 M phosphate buffer, pH 7, with the nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-adenosine 2',5'-bisphosphate (2-BDB-TA 2',5'-DP) to give 78% inactivation. Protection against inactivation was achieved with NADPH, indicating that modification occurred in the region of the coenzyme binding site. After reaction of the enzyme with 2-BDB-TA 2',5'-DP, the dioxo moiety of the bound reagent was reduced with [3H]NaBH4. The radioactive peptide which corresponds to the sequence Leu282-Cys283-Glu284-Ile285-Lys286 was isolated by HPLC from tryptic digests of inactive modified enzyme but was absent in digests of active enzyme modified in the presence of NADPH. Mutant enzyme E284Q was 64% inactived by 2-BDB-TA 2',5'-DP and modification of the corresponding Leu282-Lys286 peptide was found, while neither mutant enzyme C283I nor C283I:E284Q was inactivated by the nucleotide analogue and no corresponding radioactive peptides were found. These results show that cysteine-283 is the target of the reagent and is located near the coenzyme binding site. The nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A 2',5'-DP) has also been shown to react with cysteine-283 (L. Haeffner-Gormley et al., 1991, J. Biol. Chem. 266, 5388-5394). However, the predominant form of the Leu282-Lys286 peptide after reaction with 2-BDB-TA 2',5'-DP contained only 0.17 mol tritium/mol leucine, whereas the 2-BDB-T epsilon A 2',5'-DP-modified peptide contained 1.80 mol tritium/mol leucine; these results indicate that the reaction product of 2-BDB-T epsilon A 2',5'-DP retains two reducible carbonyl groups while these are not available in the product of 2-BDB-TA 2',5'-DP. It is suggested that cysteine-283 reacts primarily at a carbonyl group of 2-BDB-TA 2',5'-DP to form a thiohemiacetal derivative, while it reacts at the methylene group of 2-BDB-T epsilon A 2',5'-DP with displacement of bromide. Both nucleotide analogues also yielded, in small amount, a crosslinked peptide containing the sequences 282-286 and 299-333, indicating proximity between these regions in the native structure.
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Affiliation(s)
- L Haeffner-Gormley
- Department of Chemistry and Biochemistry, University of Delaware, Newark 19716
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9
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Haeffner-Gormley L, Chen ZD, Zalkin H, Colman RF. Evaluation of cysteine 283 and glutamic acid 284 in the coenzyme binding site of Salmonella typhimurium glutamate dehydrogenase by site-directed mutagenesis and reaction with the nucleotide analogue 2-[4-bromo-2,3-dioxobutyl)thio)-1,N6-ethenoadenosine 2‘,5‘-bisphosphate. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67606-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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10
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Papadopoulou D, Louis C. The gene coding for glutamate dehydrogenase inDrosophila melanogaster. Biochem Genet 1990. [DOI: 10.1007/bf00554064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Papadopoulou D, Louis C. The gene coding for glutamate dehydrogenase in Drosophila melanogaster. Biochem Genet 1990; 28:337-46. [PMID: 1702620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have isolated the Drosophila melanogaster locus coding for L-glutamate dehydrogenase (EC 1.4.1.3) by virtue of its similarity to the corresponding human gene. There is only one copy of this gene in the fruit fly genome, located on the right arm of chromosome 3 (95D1-4). The transcript includes at least one large intron and matures to a approximately 2.4-kb-long polyadenylated RNA whose expression is under developmental control.
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Affiliation(s)
- D Papadopoulou
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology, Hellas, Crete, Greece
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12
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13
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Takeda Y, Nakajyoh Y, Isshiki S. Cloning and expression in Escherichia coli of the glutamate dehydrogenase gene, gdh, from Corynebacterium melassecola. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/0922-338x(90)90236-p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Bansal A, Dayton MA, Zalkin H, Colman RF. Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2′,5′-bisphosphate. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)81733-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Bascomb NF, Prunkard DE, Schmidt RR. Different Rates of Synthesis and Degradation of Two Chloroplastic Ammonium-Inducible NADP-Specific Glutamate Dehydrogenase Isoenzymes during Induction and Deinduction in Chlorella sorokiniana Cells. PLANT PHYSIOLOGY 1987; 83:85-91. [PMID: 16665221 PMCID: PMC1056303 DOI: 10.1104/pp.83.1.85] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The kinetics of accumulation (per milliliter of culture) of the alpha- and beta- subunits, associated with chloroplast-localized ammonium inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH) isoenzymes, were measured during a 3 hour induction of synchronized daughter cells of Chlorella sorokiniana in 29 millimolar ammonium medium under photoautotrophic conditions. The beta-subunit holoenzyme(s) accumulated in a linear manner for 3 hours without an apparent induction lag. A 40 minute induction lag preceded the accumulation of the alpha-subunit holoenzyme(s). After 120 minutes, the alpha-subunit ceased accumulating and thereafter remained at a constant level (i.e. steady state between synthesis and degradation). From pulsechase experiments, using (35)SO(4) and immunochemical procedures, the rate of synthesis of the alpha-subunit was shown to be greater than the beta-subunit during the first 80 minutes of induction. The alpha- and beta-subunits had different rates of degradation during the induction period (t((1/2)) = 50 versus 150 minutes, respectively) and during the deinduction period (t((1/2)) = 5 versus 13.5 minutes) after removal of ammonium from the culture. During deinduction, total NADP-GDH activity decreased with a half-time of 9 minutes. Cycloheximide completely inhibited the synthesis and degradation of both subunits. A model for regulation of expression of the NADP-GDH gene was proposed.
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Affiliation(s)
- N F Bascomb
- Department of Microbiology and Cell Science, 1059 McCarty Hall, University of Florida, Gainesville, Florida 32611
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17
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Hill-Chappell JM, Spector MP, Foster JW. The pyridine nucleotide cycle of Salmonella typhimurium: genetic characterization of the pncXA operon. MOLECULAR & GENERAL GENETICS : MGG 1986; 205:507-14. [PMID: 3550386 DOI: 10.1007/bf00338090] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A series of Mud1 and Tn10 insertions were identified in the pncA chromosome region of Salmonella typhimurium which is responsible for the production of nicotinamide deamidase. Both pncA (resulting in no nicotinamide deamidase activity) and pncX (resulting in lowered nicotinamide deamidase activity) insertions were constructed. In addition, mutants which could utilize nicotinamide as a sole source of nitrogen were isolated. These mutants, designated pncH, hyperproduce nicotinamide deamidase. Genetic studies utilizing pncX--lacZ and pncA--lacZ operon fusions indicate that pncX::Tn10 insertions reduce transcription of pncA--lac while pncH mutations increase the expression of both pncA--lacZ and pncX-lacZ. The gene order was determined as purB--pncA--pncX--gdh with transcription of both pncA and pncX occurring in the counterclockwise direction. Merodiploid studies suggest a model whereby pncX and pncA form an operon with the major promoter occurring upstream from pncX. A second, weaker promoter for pncA must be situated between pncX and pncA. The pncH mutations appear to occur in the pncX promoter (pncXp) increasing promoter activity.
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18
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Gurr SJ, Hawkins AR, Drainas C, Kinghorn JR. Isolation and identification of the Aspergillus nidulans gdhA gene encoding NADP-linked glutamate dehydrogenase. Curr Genet 1986; 10:761-6. [PMID: 2834076 DOI: 10.1007/bf00405099] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The Neurospora crassa am gene was used as a heterologous probe to identify clones from two independently constructed Aspergillus nidulans gene libraries. These clones have a common HindIII 1.85 kb fragment. This A. nidulans nucleotide stretch hybridises to a N. crassa 2.7 kb BamHI fragment of wild type DNA but not to a co-migrating fragment from the DNA of the N. crassa am132 deletion mutant. One A. nidulans clone was shown to complement the N. crasse am132 deletion strain. The N. crassa transformants show low levels (approximately 5%) of heterologous glutamate dehydrogenase activity. The A. nidulans gdhA gene was found to locate in N. crassa at both the "homologous" (i.e. am) site as well as non-homologous sites. Partial nucleotide analysis of the fragment has revealed the 5' end of the locus and considerable homology with the N. crassa am gene. We concluded that we have cloned the A. nidulans gdhA gene.
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Affiliation(s)
- S J Gurr
- Department of Biochemistry and Microbiology, University of St. Andrews, St. Andrews Fife, UK
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Mountain A, McPherson MJ, Baron AJ, Wootton JC. The Klebsiella aerogenes glutamate dehydrogenase (gdhA) gene: cloning, high-level expression and hybrid enzyme formation in Escherichia coli. MOLECULAR & GENERAL GENETICS : MGG 1985; 199:141-5. [PMID: 2987645 DOI: 10.1007/bf00327523] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The NADP-dependent glutamate dehydrogenase gene of Klebsiella aerogenes was cloned in E. coli in the expression plasmid pRK9. The cloned gene shows a high level of expression in E. coli in the hybrid plasmid pKG3 and such expression is independent of the vector promoter, as shown by experiments in which the promoter was deleted. Active hybrid GDH hexamers were shown in cell-free extracts of an E. coli strain carrying cloned gdhA genes of both E. coli and K. aerogenes. The nucleotide sequence of the N-terminal coding region of the K. aerogenes gdhA gene was determined and found to be strongly homologous with that of E. coli.
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Neuhard J, Stauning E, Kelln RA. Cloning and characterization of the pyrE gene and of PyrE::Mud1 (Ap lac) fusions from Salmonella typhimurium. EUROPEAN JOURNAL OF BIOCHEMISTRY 1985; 146:597-603. [PMID: 3882417 DOI: 10.1111/j.1432-1033.1985.tb08693.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A lambda-specialized transducing phage carrying the pyrE gene from Salmonella typhimurium LT2 was constructed and used as the source of DNA for subcloning the pyrE gene into pBR322. The pyrE gene product was identified as a 23-kDa polypeptide using a minicell system for analysis of plasmid-encoded proteins. Studies utilizing a promoter-cloning vehicle provided evidence for the existence of two promoter regions, one located close to the start of the structural gene and the other positioned more than 300 base pairs upstream. Transcription from the more distal promotor was the only situation in which significant regulation by pyrimidines was observed. Additional studies served to localize sites involved in the regulation of pyrE expression and led to the inference that regulation does not occur at the level of initiation of transcription. A procedure was developed for the construction of plasmids through recombination in vivo, whereby pyrE::Mud1 (Ap lac) fusions were transferred to a recipient pyrE+ plasmid by bacteriophage P22-mediated transduction. This enabled the identification of the integration sites of Mud within pyrE and also verified the deduced orientation of the pyrE gene in the parental plasmid. The nucleotide sequence of the 5' end of the pyrE gene was determined, including 150 nucleotide residues encoding the first 50 N-terminal amino acids of orotate phosphoribosyltransferase, and 400 nucleotides upstream from the start of the coding region. The leader region contains sequences characteristic of a rho-independent transcriptional terminator preceded by a cluster of thymidylate residues. In addition, the leader RNA contains an open reading frame with a UGA stop codon immediately preceding the putative transcriptional terminator. The nucleotide sequence suggests that pyrE expression is regulated by modulated attenuation, as has been proposed to be the case for both pyrB and pyrE expression in Escherichia coli.
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Madonna MJ, Fuchs RL, Brenchley JE. Fine structure analysis of Salmonella typhimurium glutamate synthase genes. J Bacteriol 1985; 161:353-60. [PMID: 3881392 PMCID: PMC214879 DOI: 10.1128/jb.161.1.353-360.1985] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Glutamate synthase activity is required for the growth of Salmonella typhimurium on media containing a growth-rate-limiting nitrogen source. Mutations that alter glutamate synthase activity had been identified in the gltB gene, but it was not known which of the two nonidentical subunits of the enzyme was altered. To examine the gene-protein relationship of the glt region, two nonsense mutations were identified and used to demonstrate that gltB encodes the large subunit of the enzyme. Six strains with independent Mu cts d1 (lac bla) insertions were isolated, from which a collection of deletion mutations was obtained. The deletions were transduced with the nonsense mutations and 38 other glt point mutations to construct a fine-structure genetic map. Chromosome mobilization studies, mediated by Hfr derivatives of Mu cts d1 lysogens, showed that gltB is transcribed in a clockwise direction, as shown in the S. typhimurium linkage map. Studies of the polar effects of three Mu cts d1 insertions indicated that the gene for the small subunit maps clockwise to gltB and that the two genes are cotranscribed to form a glt operon.
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