Molecular cloning and sequence of the cytoplasmic ribosomal protein S15a gene from Agaricus bisporus

We have isolated an Agaricus bisporus cDNA which encodes an open reading frame of 130 amino acids. A comparison with the Genbank database shows that the deduced amino acid sequence of this open reading frame is highly homologous to the small subunit ribosomal proteins S15a of Brassica napus and Drosophila melanogaster and to the small subunit ribosomal proteins S24 of Strongylocentrotus purpuratus and Saccharomyces cerevisiae.

Purification and characterization of NADP-dependent glutamate dehydrogenase from the commercial mushroom Agaricus bisporus

The nicotinamide adenine dinucleotide phosphate (NADP)-dependent glutamate dehydrogenase (NADP-GDH) of Agaricus bisporus, a key enzyme in ammonia assimilation, was purified to apparent electrophoretic homogeneity with 27% recovery of the initial activity. The molecular weight of the native enzyme was 330 kDa. The enzyme is probably a hexamer, composed of identical subunits of 48 kDa. The isoelectric point of the enzyme was found at pH 4.8. The N-terminus appeared to be blocked. The enzyme was specific for NADP(H). The Km-values were 2.1, 3.2, 0.074, 27.0, and 0.117 mM for ammonia, 2-oxoglutarate, NADPH, L-glutamate, and NADP respectively. The pH optima for the amination and deamination reactions were found to be 7.6 and 9.0, respectively. The temperature optimum was 33 degrees C. The effect of several metabolites on the enzyme's activity was tested. Pyruvate, oxaloacetate, ADP, and ATP showed some inhibitory effect. Divalent cations slightly stimulated the aminating reaction. Antibodies raised against the purified enzyme were able to precipitate NADP-GDH activity from a cell-free extract in an anticatalytic immunoprecipitation test. Analysis of a Western blot showed the antibodies to be specific for NADP-GDH.

Cloning, characterization and expression of pepF, a gene encoding a serine carboxypeptidase from Aspergillus niger

We have cloned a gene (pepF) encoding a serine carboxypeptidase, proteinase F (PEPF), from Aspergillus niger. The sequences were identified in a phage lambda genomic DNA library using a synthetic probe based on the N-terminal sequence of PEPF. Nucleotide sequence data from pepF genomic and cDNA clones reveals that it is composed of four exons of 199, 283, 227 and 881 bp, interrupted by three introns of 53, 69 and 59 bp. The sequence of pepF codes for a polypeptide of 530 amino acids (aa), of which the first 52 aa are not present in the mature PEPF. This region may represent a prepro sequence that is removed by proteolytic cleavage as a monobasic cleavage site (Lys52). Northern blot analysis of total cellular RNA extracted from A. niger cells indicates that pepF is transcribed as a single 1.8-kb mRNA, which is regulated by nitrogen and carbon repression, specific induction and the pH of the culture medium.

Upregulation of antithrombotic ectonucleotidases by aspirin in human endothelial cells in-vitro

Ecto ATP-diphosphohydrolase (apyrase) activity of human endothelial cells following aspirin treatment has been studied in-vitro. It was shown by HPLC analysis of supernatant samples that pre-incubation of the cultures with aspirin resulted in a significantly increased turnover of supplemented ATP into its degradation products (ADP and AMP). Enhanced expression of ectoenzyme after aspirin treatment could be observed as demonstrated by immunofluorescence-staining with monoclonal anti-apyrase antibodies. This suggests enhancement of endothelial ATP-diphosphohydrolase activity induced by aspirin. The present data obtained in human vascular cells in-vitro are in line with results from previous animal studies in-vivo, suggesting a novel cyclooxygenase-independent antithrombotic activity of aspirin.

Extracellular arabinases in Aspergillus nidulans: the effect of different cre mutations on enzyme levels

The regulation of the syntheses of two arabinan-degrading extracellular enzymes and several intracellular L-arabinose catabolic enzymes was examined in wild-type and carbon catabolite derepressed mutants of Aspergillus nidulans. alpha-L-Arabinofuranosidase B, endoarabinase, L-arabinose reductase, L-arabitol dehydrogenase, xylitol dehydrogenase, and L-xylulose reductase were all inducible to varying degrees by L-arabinose and L-arabitol and subject to carbon catabolite repression by D-glucose. With the exception of L-xylulose reductase, all were clearly under the control of creA, a negative-acting wide domain regulatory gene mediating carbon catabolite repression. Measurements of intracellular enzyme activities and of intracellular concentrations of arabitol and xylitol in mycelia grown on D-glucose in the presence of inducer indicated that carbon catabolite repression diminishes, but does not prevent uptake of inducer. Mutations in creA resulted in an apparently, in some instances very marked, elevated inducibility, perhaps reflecting an element of "self" catabolite repression by the inducing substrate. creA mutations also resulted in carbon catabolite derepression to varying degrees. The regulatory effects of a mutation in creB and in creC, two genes whose roles are unclear, but likely to be indirect, were, when observable, more modest. As with previous data showing the effect of creA mutations on structural gene expression, there were striking instances of phenotypic variation amongst creA mutant alleles and this variation followed no discernible pattern, i.e. it was non-hierarchical. This further supports molecular data obtained elsewhere, indicating a direct role for creA in regulating structural gene expression, and extends the range of activities under creA control.

Enzymes of glucose and methanol metabolism in the actinomycete Amycolatopsis methanolica

The actinomycete Amycolatopsis methanolica was found to employ the normal bacterial set of glycolytic and pentose phosphate pathway enzymes, except for the presence of a PPi-dependent phosphofructokinase (PPi-PFK) and a 3-phosphoglycerate mutase that is stimulated by 2,3-bisphosphoglycerate. Screening of a number of actinomycetes revealed PPi-PFK activity only in members of the family Pseudonocardiaceae. The A. methanolica PPi-PFK and 3-phosphoglycerate mutase enzymes were purified to homogeneity. PPi-PFK appeared to be insensitive to the typical effectors of ATP-dependent PFK enzymes. Nevertheless, strong N-terminal amino acid sequence homology was found with ATP-PFK enzymes from other bacteria. The A. methanolica pyruvate kinase was purified over 250-fold and characterized as an allosteric enzyme, sensitive to inhibition by P(i) and ATP but stimulated by AMP. By using mutants, evidence was obtained for the presence of transketolase isoenzymes functioning in the pentose phosphate pathway and ribulose monophosphate cycle during growth on glucose and methanol, respectively.

Crystallization and preliminary crystallographic characterization of endo-polygalacturonase II from Aspergillus niger

The endo-polygalacturonase II from Aspergillus niger has been crystallized from an ammonium sulfate solution by the hanging drop method. The crystals belong to the monoclinic space group P2(1), with cell dimensions a = 69.6 A, b = 152.6 A, c = 74.0 A and beta = 91.2 degrees with four molecules per asymmetric unit. The crystals diffract to at least 2.8 A resolution and are suitable for X-ray analysis.

Characterization of an Aspergillus nidulans L-arabitol dehydrogenase mutant

The degradation pathway for L-arabinose, which consists of a sequence of alternating reduction and oxidation reactions prior to ultimate phosphorylation, was studied in Aspergillus nidulans wild-type as well as in an L-arabinose non-utilizing mutant. The inability of the mutant to use L-arabinose was caused by the absence of L-arabitol dehydrogenase activity. The effect of the mutation on polyol accumulation patterns was studied upon growth on various carbon sources. The presence of L-arabinose resulted in intracellular accumulation of arabitol in this mutant. Moreover, the mutant secreted arabitol under these conditions and, in contrast to the wild-type, featured enhanced expression of enzymes involved in L-arabinose catabolism as well as of extracellular glycosyl hydrolases involved in degradation of the plant cell wall polysaccharide L-arabinan.

Arabinase gene expression in Aspergillus niger: indications for coordinated regulation

Aspergillus niger secretes three glycosylated glycosyl hydrolases which are involved in degradation of the plant cell wall polysaccharide L-arabinan: alpha-L-arabinofuranosidases (ABF) A and B, and endo-1,5-alpha-L-arabinase (ABN) A. The nucleotide sequence of the previously cloned gene encoding ABF A (abfA) from A. niger was determined. The coding region contains seven introns. Mature ABF A comprises 603 amino acids with a molecular mass of 65.4 kDa as deduced from the nucleotide sequence. The secreted enzyme is N-glycosylated. The primary structures of the three A. niger arabinases characterized lack similarity. Regulation of arabinase expression upon induction by sugar beet pulp and by L-arabitol was studied as a function of time. This was done in wild-type A. niger as well as in transformants carrying multiple copies of either one of the ABF-encoding genes. Each arabinase gene responded differently upon a mycelial transfer to L-arabitol-containing medium. Extra copies of abfA or abfB led to a decreased expression level of ABN A, though the repression elicited by abfB is stronger and more persistent than that effected by abfA. Multiple copies of both abf genes influence expression of the other ABF similarly, but to a far less pronounced degree than they affect ABN A synthesis. Four putative promoter elements, shared by all three arabinase genes, could be involved in coordination of L-arabinan degradation by A. niger.

Regulation of the xylanase-encoding xlnA gene of Aspergillus tubigensis

A gene encoding an endo-1,4-beta-xylanase from Aspergillus tubigensis was cloned by oligonucleotide screening using oligonucleotides derived from amino acid sequence data obtained from the purified protein. The isolated gene was functional as it could be expressed in the very closely related fungus Aspergillus niger. The xylanase encoded by this gene is synthesized as a protein of 211 amino acids. After cleavage of the presumed prepropeptide this results in a mature protein of 184 amino acids with a molecular weight of 19 kDa and an isoelectric point of 3.6. The regulatory region of the xlnA gene was studied with respect to the response to xylan induction and carbon catabolite repression. By deletion analysis of the 5' upstream region of the gene a 158 bp region involved in the xylan specific induction was identified. To study this regulatory element a reporter system for transcriptional activating sequences was developed that is based on the A. niger glucose oxidase-encoding gene. From the results with this reporter system it is concluded that this 158 bp fragment not only contains the information required for induction of transcription but that it also plays a role in carbon catabolite repression of the xlnA gene. The region directly upstream of this fragment contains four potential CREA target sites; deletion of this region leads to an increase in the level of transcription. These results suggest that carbon catabolite repression of the xlnA gene is controlled at two levels, directly by repression of xlnA gene transcription and indirectly by repression of the expression of a transcriptional activator. This type of mechanism would be similar to the double lock mechanism for the regulation of gene expression of alcA in Aspergillus nidulans. The reporter system was also used to study the regulation of expression via the functions located on this fragment in A. niger and in A. nidulans. Essentially the same pattern of regulation was found in both of these hosts. Therefore, regulation of xylanase gene expression is basically conserved in all three aspergilli.

Does aminophylline benefit adults admitted to the hospital for an acute exacerbation of asthma?

OBJECTIVE

To determine the effect of adding intravenous theophylline (administered as aminophylline) to nebulizations of albuterol and intravenous methylprednisolone in adults hospitalized for acute asthma.

DESIGN

Randomized, placebo-controlled, double-blind study.

SETTING

Inpatient service of a tertiary-care, university teaching hospital.

PATIENTS

21 adults (22 to 48 years old)--10 in the aminophylline group and 11 in the placebo group.

INTERVENTIONS

Nebulized albuterol, 2.5 or 5.0 mg every 0.5 to 4 hours; intravenous methylprednisolone, 60 mg every 6 hours; and either individualized doses of aminophylline or placebo for 48 hours.

MEASUREMENTS

Forced expiratory volume in 1 second (FEV1), the number of "as needed" albuterol nebulizations and total dose, asthma symptom scores, and adverse effects.

RESULTS

At admission from the emergency department, the mean +/- SD baseline FEV1 was 49% +/- 19% of the predicted value in the aminophylline group and 43% +/- 13% of the predicted value in the placebo group. The improvement in FEV1 at 3 hours was greater in the aminophylline group (29% +/- 23% compared with 10% +/- 10% in the placebo group; mean difference, 19 percentage points; 95% CI, 3 to 35 percentage points; P = 0.023). At 48 hours, FEV1 was 75% +/- 19% of the predicted value in the aminophylline group and 58% +/- 15% of the predicted value in the placebo group (mean difference, 17 percentage points; CI, 0.2 to 34.8 percentage points; P = 0.048). Aminophylline-treated patients required fewer nebulizations of albuterol (10.3 +/- 3.8 compared with 16.4 +/- 5.3; mean difference, -6.1; CI, -10.3 to -1.8) and less total dosage (34 +/- 16 mg compared with 70 +/- 34 mg; mean difference, -36 mg; CI, -60.6 to -11.3 mg P = 0.02). No statistical differences were observed in asthma symptom scores or frequency of adverse effects.

CONCLUSIONS

Individualized doses of intravenous theophylline added to frequent nebulizations of albuterol and intravenous methylprednisolone appear to benefit adults admitted to the hospital with acute asthma and are well tolerated when serum concentrations are maintained in the therapeutic range.

Cloning and characterization of the abfB gene coding for the major alpha-L-arabinofuranosidase (ABF B) of Aspergillus niger

Based on amino-acid sequence data from Aspergillus niger alpha-L-arabinofuranosidase B (ABF B), and cyanogen bromide fragments derived thereof, deoxyoligonucleotide mixtures were designed to be employed as primers in a polymerase chain reaction (PCR) on A. niger genomic DNA. This resulted in amplification of three related PCR products. The abfB gene encoding ABF B was isolated from a genomic library using such an amplification product as a probe. A 5.1-kb BamHI fragment was subcloned to result in plasmid pIM991. Upon introduction by co-transformation into both A. niger and A. nidulans uridine auxotrophic strains, pIM991 was shown to contain the functional gene since prototrophic transformants overproduced ABF B upon growth on the inducing carbon source sugar beet pulp. A plate assay was developed enabling quick selection of ABF B-overproducing transformants. The sequence of a 4122-bp long BamHI/SstI fragment was determined. The abfB gene does not contain introns and codes for a protein of 499 amino acids. The mature ABF B, 481 amino acids in length, has a deduced molecular weight of 50.7 kDa. A. niger abfB is the first eukaryotic gene encoding an ABF to be characterized.

Molecular cloning, expression and structure of the endo-1,5-alpha-L-arabinase gene of Aspergillus niger

Secretion of endo-1,5-alpha-L-arabinase A (ABN A) by an Aspergillus niger xylulose kinase mutant upon mycelium transfer to medium containing L-arabitol was immunochemically followed with time to monitor its induction profile. A cDNA expression library was made from polyA+ RNA isolated from the induced mycelium. This library was immunochemically screened and one ABN A specific clone emerged. The corresponding abnA gene was isolated from an A. niger genomic library. Upon Southern blot analysis, a 3.1-kb HindIII fragment was identified and subcloned to result in plasmid pIM950. By means of co-transformation using the A. niger pyrA gene as selection marker, the gene was introduced in both A. niger and A. nidulans uridine auxotrophic mutants. Prototrophic A. niger and A. nidulans transformants overproduced A. niger ABN A upon growth in medium containing sugar beet pulp as the sole carbon source, thereby establishing the identity and functionality of the cloned gene. The DNA sequence of the complete HindIII fragment was determined and the structure of the abnA gene as well as of its deduced gene product were analysed. Gene abnA contains three introns within its structural region and codes for a protein of 321 amino acids. Signal peptide processing results in a mature protein of 302 amino acids with a deduced molecular mass of 32.5 kDa. A. niger abnA is the first gene encoding an ABN to be isolated and characterized.

Induction of glucose oxidase, catalase, and lactonase in Aspergillus niger

The induction of glucose oxidase, catalase, and lactonase activities was studied both in wild-type and in glucose oxidase regulatory and structural mutants of Aspergillus niger. The structural gene for glucose oxidase was isolated and used for Northern analysis and in transformation experiments using various gox mutations. Wild-type phenotype could be restored in the glucose oxidase-negative mutant (goxC) by transformation with the structural gene. We conclude, therefore, that the goxC marker which is located on chromosome 2 represents the structural gene of glucose oxidase. Glucose and a high oxygen level are necessary for the induction of all three enzyme activities in the wild-type strain and it was shown that both glucose and oxygen effects reflect regulation at the transcriptional level. The goxB mutation results in constitutive expression of all three activities although modulated to some extent by the carbon source. The goxE mutation only has an effect on lactonase and glucose oxidase expression and does not relieve the necessity for a high oxygen level. Catalase and lactonase could not be induced in the glucose oxidase-negative strain (goxC). Addition of H2O2 resulted in the induction of all three enzymes in the wild-type without glucose being present. The H2O2 induction is probably mediated by the goxB product. Besides the H2O2 induction there is still an effect of the carbon source on the induction. A model for induction of glucose oxidase, catalase, and lactonase in A. niger is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Arabinan degrading enzymes from Aspergillus nidulans: induction and purification

The presence in Aspergillus nidulans of two enzymes related to the Aspergillus niger endo-arabinase and alpha-L-arabinofuranosidase B has been established using antibodies against the purified A. niger enzymes. Moreover, the absence of an equivalent in A. nidulans to the alpha-L-arabinofuranosidase A of A. niger has been confirmed both at the protein and at the DNA level. Both A. nidulans arabinases have been purified and physico-chemically and kinetically characterized. They have a much higher temperature optimum than the corresponding A. niger enzymes. The pattern of induction has been studied on media containing different carbon sources showing an important role of L-arabitol in the induction of these enzymes.

Characterization of the pyruvate kinase-encoding gene (pki1) of Trichoderma reesei

The pyruvate kinase-encoding gene (pki1) from Trichoderma reesei was isolated by hybridization to the corresponding Aspergillus nidulans pkiA gene. The 1614-bp nucleotide (nt) sequence of the cloned gene codes for a 538-amino-acid protein. The coding sequence contains a single intron of 246 nt at a position identical to that of intron E in the A. nidulans gene. The PKI protein shows extensive homology to the PKIs of A. nidulans and A. niger (67%) and Saccharomyces cerevisiae (59%). The 5' non-coding sequence contains a number of motifs typical for yeast glycolytic genes, but so far only rarely found in filamentous fungi.

Cloning of the Aspergillus niger gene encoding alpha-L-arabinofuranosidase A

Using L-arabitol as an inducer, simple induction conditions were established that resulted in high-level expression of alpha-L-arabinofuranosidase A by an Aspergillus niger D-xylulose kinase mutant strain. These conditions were adapted to construct a cDNA expression library from which an alpha-L-arabinofuranosidase A cDNA clone was isolated using specific antiserum. The corresponding gene encoding alpha-L-arabinofuranosidase A (abfA) was isolated from a genomic library and cloned into a high copy plasmid vector. By co-transformation of uridine auxotrophic mutants lacking orotidine-5-phosphate decarboxylase activity, the afbA gene was introduced both in A. niger and A. nidulans, using the A. niger pyrA gene as selection marker. The identity of the abfA gene was confirmed by overexpression of the gene product by A. niger and A. nidulans transformants, upon growth using sugar beet pulp as the carbon source.

Effect of different positively charged amino acids, C-terminally of the signal peptidase cleavage site, on the translocation kinetics of a precursor protein in Escherichia coli K-12

Introduction of positively charged amino acids immediately downstream of the signal sequence in prokaryotic precursor proteins is known to affect the export process. However, it is not clear whether different positively charged amino acids affect the export process similarly. To investigate this, the glutamate at position +2 of outer membrane protein PhoE was substituted by arginine, lysine or histidine. Pulse-chase experiments revealed that the Lys and Arg residues at position +2 caused a reduced processing rate, and that the effect was markedly more severe in the case of the Arg residue. Trypsin accessibility experiments revealed that the accumulated precursors were present in the cytoplasm. Since the degree of the inhibitory effect corresponded to the pKa of the different positively charged amino acids, this suggests that the positively charged residues must be deprotonated during the secretory process.

Induction of extracellular arabinases on monomeric substrates in Aspergillus niger

The induction of extracellular arabinases by pentose sugars and polyols generated by the metabolic pathway of L-arabinose and D-xylose catabolism in Aspergillus niger was investigated. Induction occurred with L-arabinose and L-arabitol but not with D-xylose or xylitol. L-arabitol in particular was found to be a good inducer for alpha-L-arabinofuranosidase and endo-arabinase activities. Western blotting analysis showed both alpha-L-arabinofuranosidase A and B to be present. No induction was observed using D-arabitol. Unlike the wild type A. niger N402 strain, the A. niger xylulose kinase negative mutant N572 also showed induction of alpha-L-arabinofuranosidases A and B and endo-arabinase activity on D-xylose and xylitol. This is due to metabolic conversion of these compounds leading to the accumulation of both xylitol and L-arabitol in this mutant, the latter of which then acts as inducer. The induction of the two alpha-L-arabinofuranosidases and endo-arabinase is under the control of two regulatory systems namely pathway specific induction and carbon catabolite repression. Under derepressing conditions in the wild type only alpha-L-arabinofuranosidase B could be detected by Western blotting analysis. This indicates that alpha-L-arabinofuranosidase B is of importance in the initiation of specific induction of the various arabinose activities in A. niger grown on arabinose containing structural polysaccharides.

Topology of PhoE porin: the 'eyelet' region

A model for the topology of the PhoE porin has been proposed according to which the polypeptide traverses the outer membrane sixteen times mostly as amphipathic beta-sheets, thereby exposing eight loops at the cell surface. Until now, no evidence has been obtained for the surface exposure of the third loop. Recently, the structure of porin of Rhodobacter capsulatus has been determined. The proposed model of PhoE is very similar to the structure of the R. capsulatus porin, which has an 'eyelet' region, extending into the interior of the pore. The proposed third external loop of PhoE might form a similar 'eyelet' region. To determine the location of the predicted third external loop of PhoE, multiple copies of an oligonucleotide linker encoding an antigenic determinant of VP1 protein of foot-and-mouth disease virus (FMDV) were inserted. All hybrid proteins were properly inserted in the outer membrane. The monoclonal antibody MA11, directed against the linear FMDV epitope, was able to bind only to intact cells expressing a hybrid PhoE protein with at least three copies of the FMDV epitope present. Antibiotic sensitivity tests and single-channel conductance measurements revealed that the insertions influenced the channel size. These results are consistent with a location of the third loop of PhoE within the pore channel.

Clearance of indomethacin occurs predominantly by renal glucuronidation

In this report we describe the conditions of collection, storage and handling of urine samples, collected after oral dosing with indomethacin in man, in order to maintain the integrity of the labile glucuronide formed. We found that the body clearance occurs predominantly by renal metabolism, due to glucuronidation in the human kidney. These glucuronides may be converted to isomeric glucuronides and/or the parent compound indomethacin during the residence time in the bladder.