scholarly journals A Novel Gene Encoding Xanthan Lyase of Paenibacillus alginolyticus Strain XL-1

2000 ◽  
Vol 66 (9) ◽  
pp. 3945-3950 ◽  
Author(s):  
Harald J. Ruijssenaars ◽  
Sybe Hartmans ◽  
Jan C. Verdoes
Keyword(s):  
Signal Sequence ◽  
Fold Increase ◽  
Side Chain ◽  
Cloning And Sequencing ◽  
Gene Encoding ◽  
E Coli ◽  
Mature Enzyme ◽  
Locust Bean ◽  
Encoding Gene ◽  
Amino Acid Signal

ABSTRACT Xanthan-modifying enzymes are powerful tools in studying structure-function relationships of this polysaccharide. One of these modifying enzymes is xanthan lyase, which removes the terminal side chain residue of xanthan. In this paper, the cloning and sequencing of the first xanthan lyase-encoding gene is described, i.e., thexalA gene, encoding pyruvated mannose-specific xanthan lyase of Paenibacillus alginolyticus XL-1. ThexalA gene encoded a 100,823-Da protein, including a 36-amino-acid signal sequence. The 96,887-Da mature enzyme could be expressed functionally in Escherichia coli. Like the native enzyme, the recombinant enzyme showed no activity on depyruvated xanthan. Compared to production by P. alginolyticus, a 30-fold increase in volumetric productivity of soluble xanthan lyase was achieved by heterologous production in E. coli. The recombinant xanthan lyase was used to produce modified xanthan, which showed a dramatic loss of the capacity to form gels with locust bean gum.

scholarly journals SHV-16, a β-Lactamase with a Pentapeptide Duplication in the Omega Loop

2001 ◽  
Vol 45 (9) ◽  
pp. 2480-2485 ◽  
Author(s):  
Corinne Arpin ◽  
Roger Labia ◽  
Catherine Andre ◽  
Cécile Frigo ◽  
Zoubida El Harrif ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Donor Cell ◽  
Fold Increase ◽  
Site Directed Mutagenesis ◽  
Resistance Pattern ◽  
E Coli ◽  
Omega Loop ◽  
Low Levels ◽  
Encoding Gene ◽  
Level Resistance

ABSTRACT A clinical isolate of Klebsiella pneumoniae was found to be resistant to ampicillin (MIC of 128 μg/ml), ticarcillin (MIC of 512 μg/ml), and ceftazidime (MIC of 128 μg/ml) and susceptible to all other β-lactams; a synergistic effect between clavulanate and ceftazidime suggested the presence of an extended-spectrum β-lactamase (ESBL). Transconjugants inEscherichia coli were obtained at low levels (10−7 per donor cell) and exhibited a similar β-lactam resistance pattern (resistant to ampicillin, ticarcillin, and ceftazidime at 64 μg/ml). The ESBL, pI 7.6, was encoded by a large plasmid (>100 kb) which did not carry any other resistance determinant. The ESBL-encoding gene was amplified by PCR usingbla SHV-specific primers and was sequenced. The deduced amino acid sequence of the SHV-16 ESBL showed that it differed from SHV-1 by only a pentapeptide insertion (163DRWET167) corresponding to a tandem duplication in the omega loop. The implication of the 163a-DRWET163b-DRWET sequence in ceftazidime resistance was confirmed by cloning either bla SHV-1 orbla SHV-16 in the same vector, subsequently introduced in the same E. coli strain. Under these isogenic conditions, SHV-16 conferred a 32-fold increase in ceftazidime MIC compared to that with SHV-1. Furthermore, site-directed mutagenesis experiments modifying either E166aA or E166bA revealed that the functional glutamic residue was that located in the first copy of the duplicated sequence. But surprisingly, the second E166b also conferred a low-level resistance to ceftazidime. This work is the first description of a class A enzyme exhibiting an extended substrate specificity due to an insertion instead of a nucleotide substitution(s) in a clinical isolate.

scholarly journals Variations in O-Antigen Biosynthesis and O-Acetylation Associated with Altered Phage Sensitivity in Escherichia coli 4s

2014 ◽  
Vol 197 (5) ◽  
pp. 905-912 ◽  
Author(s):  
Yuriy A. Knirel ◽  
Nikolai S. Prokhorov ◽  
Alexander S. Shashkov ◽  
Olga G. Ovchinnikova ◽  
Evelina L. Zdorovenko ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Host Cells ◽  
Side Chain ◽  
Gram Negative Bacteria ◽  
Gene Encoding ◽  
Content Type ◽  
Surface Receptors ◽  
E Coli ◽  
O Antigen ◽  
Phage Sensitivity

The O polysaccharide of the lipopolysaccharide (O antigen) of Gram-negative bacteria often serves as a receptor for bacteriophages that can make the phage dependent on a given O-antigen type, thus supporting the concept of the adaptive significance of the O-antigen variability in bacteria. The O-antigen layer also modulates interactions of many bacteriophages with their hosts, limiting the access of the viruses to other cell surface receptors. Here we report variations of O-antigen synthesis and structure in an environmentalEscherichia coliisolate, 4s, obtained from horse feces, and its mutants selected for resistance to bacteriophage G7C, isolated from the same fecal sample. The 4s O antigen was found to be serologically, structurally, and genetically related to the O antigen ofE. coliO22, differing only in side-chain α-d-glucosylation in the former, mediated by agtrlocus on the chromosome. Spontaneous mutations ofE. coli4s occurring with an unusually high frequency affected either O-antigen synthesis or O-acetylation due to the inactivation of the gene encoding the putative glycosyltransferase WclH or the putative acetyltransferase WclK, respectively, by the insertion of IS1-like elements. These mutations induced resistance to bacteriophage G7C and also modified interactions ofE. coli4s with several other bacteriophages conferring either resistance or sensitivity to the host. These findings suggest that O-antigen synthesis and O-acetylation can both ensure the specific recognition of the O-antigen receptor following infection by some phages and provide protection of the host cells against attack by other phages.

scholarly journals Aspartic Peptide Hydrolases in Salmonella enterica Serovar Typhimurium

2001 ◽  
Vol 183 (10) ◽  
pp. 3089-3097 ◽  
Author(s):  
Rachel A. Larsen ◽  
Tina M. Knox ◽  
Charles G. Miller
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Gene Encoding ◽  
E Coli ◽  
Mutant Strains ◽  
Serovar Typhimurium ◽  
Measurable Rate ◽  
Mature Enzyme ◽  
Aminopeptidase A ◽  
Peptide Hydrolases

ABSTRACT Two well-characterized enzymes in Salmonella entericaserovar Typhimurium and Escherichia coli are able to hydrolyze N-terminal aspartyl (Asp) dipeptides: peptidase B, a broad-specificity aminopeptidase, and peptidase E, an Asp-specific dipeptidase. A serovar Typhimurium strain lacking both of these enzymes, however, can still utilize most N-terminal Asp dipeptides as sources of amino acids, and extracts of such a strain contain additional enzymatic activities able to hydrolyze Asp dipeptides. Here we report two such activities from extracts of pepB pepEmutant strains of serovar Typhimurium identified by their ability to hydrolyze Asp-Leu. Although each of these activities hydrolyzes Asp-Leu at a measurable rate, the preferred substrates for both are N-terminal isoAsp peptides. One of the activities is a previously characterized isoAsp dipeptidase from E. coli, the product of theiadA gene. The other is the product of the serovar Typhimurium homolog of E. coli ybiK, a gene of previously unknown function. This gene product is a member of the N-terminal nucleophile structural family of amidohydrolases. Like most other members of this family, the mature enzyme is generated from a precursor protein by proteolytic cleavage and the active enzyme is a heterotetramer. Based on its ability to hydrolyze an N-terminal isoAsp tripeptide as well as isoAsp dipeptides, the enzyme appears to be an isoAsp aminopeptidase, and we propose that the gene encoding it be designated iaaA (isoAsp aminopeptidase). A strain lacking both IadA and IaaA in addition to peptidase B and peptidase E has been constructed. This strain utilizes Asp-Leu as a leucine source, and extracts of this strain contain at least one additional, as-yet-uncharacterized, peptidase able to cleave Asp dipeptides.

scholarly journals Detection of Ampicillin Resistance Encoding Gene of Escherichia coli from Chickens in Bandung and Purwakarta

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Kuntum Khoirani ◽  
Agustin Indrawati ◽  
Surachmi Setiyaningsih
Keyword(s):  
Diffusion Method ◽  
Antibiotics Resistance ◽  
Test Results ◽  
Chain Reaction ◽  
Gene Encoding ◽  
Disk Diffusion Method ◽  
E Coli ◽  
Polymerase Chain ◽  
Encoding Gene ◽  
Almost All

The purpose of this study was to test the resistance and to detect antibiotic resistence encoding gene in E. coli bacteria from chickens in Bandung and Purwakarta livestock. 18 E. coli isolates were tested for antibiotics resistance using the disk diffusion method. Isolates that were categorized as resistant and intermediate to antibiotics, then polymerase chain reaction was utilized to detect the resistent coding gene. The test results showed that all E. coli isolates from chickens in Bandung and Purwakarta were resistant to ampicillin (100%). E. coli isolates were still sensitive to chloramphenicol (11.1%) and gentamicin (22.2%). The gene encoding for ampC resistance from the test were in the amount of 77.7%. Sensitivity test results and detection of resistance coding gene showed that almost all isolates were resistant to ampicillin antibiotics and E. coli isolates were still sensitive to chlorampenicol and gentamicin. 

scholarly journals Secretion of mammalian ribonucleases from Escherichia coli using the signal sequence of murine spleen ribonuclease

1992 ◽  
Vol 283 (1) ◽  
pp. 137-144 ◽  
Author(s):  
C H Schein ◽  
E Boix ◽  
M Haugg ◽  
K P Holliger ◽  
S Hemmi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gene Sequence ◽  
Soluble Fraction ◽  
Signal Sequence ◽  
Pancreatic Ribonuclease ◽  
E Coli ◽  
Murine Spleen ◽  
Fermentor Culture ◽  
Trp Promoter ◽  
Amino Acid Signal

A nucleotide sequence identical with that of the recently identified murine pancreatic ribonuclease (RNAase) was isolated from a murine spleen cDNA library. Active RNAase was expressed and secreted from Escherichia coli lon-htpr- transformed with a plasmid containing the E. coli trp promoter followed by the murine RNAase gene sequence, including the original eukaryotic 26-amino-acid signal sequence. Approx. 1 mg of properly matured RNAase protein/litre was secreted into the medium of a fermentor culture after the promotor was induced by tryptophan starvation. When the signal sequence was deleted from the plasmid, intracellular RNAase activity was very low and there was no significant supernatant RNAase activity. Even higher RNAase yields were obtained with a synthetic gene for bovine pancreatic ribonuclease cloned after the signal sequence of the murine gene. About 2 mg of correctly processed RNAase A/litre was isolated from the growth medium, and a further 8-10 mg of correctly processed RNAase/litre could be isolated from the soluble fraction of the cells. Thus this eukaryotic signal sequence is both recognized by the E. coli transport and processing apparatus and gives efficient secretion, as well as export, of active, mature mammalian RNAases.

Identification of a Transcriptional Activator (ChnR) and a 6-Oxohexanoate Dehydrogenase (ChnE) in the Cyclohexanol Catabolic Pathway in Acinetobacter sp. Strain NCIMB 9871 and Localization of the Genes That Encode Them

1999 ◽  
Vol 65 (11) ◽  
pp. 5158-5162 ◽  
Author(s):  
Hiroaki Iwaki ◽  
Yoshie Hasegawa ◽  
Masahiro Teraoka ◽  
Tai Tokuyama ◽  
Hélène Bergeron ◽  
...  
Keyword(s):  
Gene Sequence ◽  
Expression System ◽  
Transcriptional Activator ◽  
Fold Increase ◽  
Gene Arrangement ◽  
Catabolic Pathway ◽  
Gene Encoding ◽  
Cyclohexanone Monooxygenase ◽  
E Coli ◽  
Molecular Masses

ABSTRACT We identified chnR, a gene encoding an AraC-XylS type of transcriptional activator that regulates the expression ofchnB, the structural gene for cyclohexanone monooxygenase (CHMO) in Acinetobacter sp. strain NCIMB 9871. The gene sequence of chnE, which encodes an NADP+-linked 6-oxohexanoate dehydrogenase, the enzyme catalyzing the fifth step of cyclohexanol degradation, was also determined. The gene arrangement ischnB-chnE-chnR. The predicted molecular masses of the three polypeptides were verified by radiolabeling by using the T7 expression system. Inducible expression of cloned chnB inEscherichia coli depended upon the presence ofchnR. A transcriptionalchnB::lacZ fusion experiment revealed that cyclohexanone induces chnB expression in E. coli, in which a 22-fold increase in activity was observed.

Pullulanase Type I from Fervidobacterium pennavorans Ven5: Cloning, Sequencing, and Expression of the Gene and Biochemical Characterization of the Recombinant Enzyme

1999 ◽  
Vol 65 (5) ◽  
pp. 2084-2091 ◽  
Author(s):  
Costanzo Bertoldo ◽  
Fiona Duffner ◽  
Per L. Jorgensen ◽  
Garabed Antranikian
Keyword(s):  
Amino Acids ◽  
Biochemical Characterization ◽  
Signal Sequence ◽  
Thermotoga Maritima ◽  
Amino Acid Identity ◽  
Type I ◽  
Start Site ◽  
Gene Encoding ◽  
Amylolytic Enzymes ◽  
E Coli

ABSTRACT The gene encoding the type I pullulanase from the extremely thermophilic anaerobic bacterium Fervidobacterium pennavorans Ven5 was cloned and sequenced in Escherichia coli. The pulA gene from F. pennavoransVen5 had 50.1% pairwise amino acid identity with pulA from the anaerobic hyperthermophile Thermotoga maritima and contained the four regions conserved among all amylolytic enzymes. The pullulanase gene (pulA) encodes a protein of 849 amino acids with a 28-residue signal peptide. The pulA gene was subcloned without its signal sequence and overexpressed in E. coli under the control of the trc promoter. This clone, E. coli FD748, produced two proteins (93 and 83 kDa) with pullulanase activity. A second start site, identified 118 amino acids downstream from the ATG start site, with a Shine-Dalgarno-like sequence (GGAGG) and TTG translation initiation codon was mutated to produce only the 93-kDa protein. The recombinant purified pullulanases (rPulAs) were optimally active at pH 6 and 80°C and had a half-life of 2 h at 80°C. The rPulAs hydrolyzed α-1,6 glycosidic linkages of pullulan, starch, amylopectin, glycogen, α-β-limited dextrin. Interestingly, amylose, which contains only α-1,4 glycosidic linkages, was not hydrolyzed by rPulAs. According to these results, the enzyme is classified as a debranching enzyme, pullulanase type I. The extraordinary high substrate specificity of rPulA together with its thermal stability makes this enzyme a good candidate for biotechnological applications in the starch-processing industry.

scholarly journals matB, a Common Fimbrillin Gene ofEscherichia coli, Expressed in a Genetically Conserved, Virulent Clonal Group

2001 ◽  
Vol 183 (16) ◽  
pp. 4727-4736 ◽  
Author(s):  
Riitta Pouttu ◽  
Benita Westerlund-Wikström ◽  
Hannu Lång ◽  
Krista Alsti ◽  
Ritva Virkola ◽  
...  
Keyword(s):  
Signal Sequence ◽  
Hypothetical Protein ◽  
Surface Expression ◽  
Gene Encoding ◽  
Clonal Group ◽  
E Coli ◽  
Significant Homology ◽  
Dna Fragment ◽  
K 12

ABSTRACT A novel fimbrial type in Escherichia coli was identified and characterized. The expression of the fimbria was associated with the O18acK1H7 clonal group of E. coli, which cause newborn meningitis and septicemia when grown at low temperature; hence, it was named the Mat (meningitis associated and temperature regulated) fimbria. The fimbriae were purified from afimA::cat sfaA::GmfliC::St derivative of the O18K1H7 isolate E. coli IHE 3034. The purified Mat fimbrillin had an apparent molecular mass of 18 kDa and did not serologically cross-react with the type 1 or S fimbria of the same strain. ThematB gene encoding the major fimbrillin was cloned from the genomic DNA of the fimA::cat sfaA::Gm fliC::St derivative of IHE 3034. The predicted MatB sequence was of 195 amino acids, contained a signal sequence of 22 residues, and did not show significant homology to any of the previously characterized fimbrial proteins. The DNA sequence of matB was 97.8% identical to a region from nucleotides 17882 to 18469 in the 6- to 8-min region of the E. coli K-12 chromosome, reported to encode a hypothetical protein. The 7-kb DNA fragment containingmatB of IHE 3034 was found by restriction mapping and partial DNA sequencing to be highly similar to the corresponding region in the K-12 chromosome. Trans complementation of thematB::cat mutation in the IHE 3034 chromosome showed that matB in combination withmatA or matC restored surface expression of the Mat fimbria. A total of 27 isolates representing K-12 strains and the major pathogroups of E. coli were analyzed for the presence of a matB homolog as well as for expression of the Mat fimbria. A conserved matB homolog was found in 25 isolates; however, expression of the Mat fimbriae was detected only in the O18acK1H7 isolates. Expression of the Mat fimbria was temperature regulated, with no or a very small amount of fimbriae or intracellular MatB fimbrillin being detected in cells cultivated at 37oC. Reverse transcriptase PCR and complementation assays with mat genes controlled by the inducibletrc promoter indicated that regulation of Mat fimbria expression involved both transcriptional and posttranscriptional events.

scholarly journals Characterization and in Vivo Cloning of prlC, a Suppressor of Signal Sequence Mutations in Escherichia coli K12

Genetics ◽  
1987 ◽  
Vol 116 (4) ◽  
pp. 513-521
Author(s):  
Nancy J Trun ◽  
Thomas J Silhavy
Keyword(s):  
Escherichia Coli ◽  
Genetic Mapping ◽  
Signal Sequence ◽  
Illegitimate Recombination ◽  
Mutant Phenotype ◽  
E Coli ◽  
Physical Location ◽  
Sequence Deletion ◽  
New Alleles

ABSTRACT The prlC gene of E. coli was originally identified as an allele, prlC1, which suppresses certain signal sequence mutations in the genes for several exported proteins. We have isolated six new alleles of prlC that also confer this phenotype. These mutations can be placed into three classes based on the degree to which they suppress the lamBsignal sequence deletion, lamBs78. Genetic mapping reveals that the physical location of the mutations in prlC correlates with the strength of the suppression, suggesting that different regions of the gene can be altered to yield a suppressor phenotype. We also describe an in vivo cloning procedure using λplacMu9H. The procedure relies on transposition and illegitimate recombination to generate a specialized transducing phage that carries prlC1. This method should be applicable to any gene for which there is a mutant phenotype.

scholarly journals Soluble Expression and Efficient Purification of Recombinant Class I Hydrophobin DewA

2021 ◽  
Vol 22 (15) ◽  
pp. 7843
Author(s):  
Sang-Oh Ahn ◽  
Ho-Dong Lim ◽  
Sung-Hwan You ◽  
Dae-Eun Cheong ◽  
Geun-Joong Kim
Keyword(s):  
Tertiary Structure ◽  
Signal Sequence ◽  
Soluble Expression ◽  
Class I ◽  
Soluble Form ◽  
Two Phase ◽  
E Coli ◽  
Small Proteins ◽  
Industrial Use ◽  
Shed Light

Hydrophobins are small proteins (<20 kDa) with an amphipathic tertiary structure that are secreted by various filamentous fungi. Their amphipathic properties provide surfactant-like activity, leading to the formation of robust amphipathic layers at hydrophilic–hydrophobic interfaces, which make them useful for a wide variety of industrial fields spanning protein immobilization to surface functionalization. However, the industrial use of recombinant hydrophobins has been hampered due to low yield from inclusion bodies owing to the complicated process, including an auxiliary refolding step. Herein, we report the soluble expression of a recombinant class I hydrophobin DewA originating from Aspergillus nidulans, and its efficient purification from recombinant Escherichia coli. Soluble expression of the recombinant hydrophobin DewA was achieved by a tagging strategy using a systematically designed expression tag (ramp tag) that was fused to the N-terminus of DewA lacking the innate signal sequence. Highly expressed recombinant hydrophobin DewA in a soluble form was efficiently purified by a modified aqueous two-phase separation technique using isopropyl alcohol. Our approach for expression and purification of the recombinant hydrophobin DewA in E. coli shed light on the industrial production of hydrophobins from prokaryotic hosts.

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