P fimbriae on uropathogenic Escherichia coli O16:K1 and O18 strains

Abstract The fimbrial composition of 12 P-fimbriate uropathogenic Escherichia coli O16 and O18 strains was analysed by immunoprecipitation with 14 fimbria-specific antisera. All the O16 strains possessed a P fimbrial serovariant with an apparent M _r of 17500. One strain had an additional, serologically closely related P fimbria with an apparent M _r of 19 800. Two groups were found among the O18 strains; one possessing a type 1C fimbria and a 19800-Da P fimbria, the other lacking type 1C fimbriae and possessing a P-fimbrial variant with an apparent M _r of 17 800. Fimbriae on strains within the groups were serologically similar by immunoprecipitation assays. Also, the fimbriae on the O16 and O18 strains were mutually cross-reactive. The grouping of the O18 strains by fimbrial serology corresponded to the previous clonal grouping based on other phenotypic characters.     

Diffusely adhering Escherichia coli (DAEC) strains of fecal origin rarely express F1845 adhesin

A total of 398 diffusely adhering Escherichia coli (DAEC) strains of fecal origin were analyzed for the presence of sequences homologous to the structural subunit gene (daaE) of the F1845 fimbria. For that purpose, a DNA fragment homologous to daaE, obtained by PCR, was used as a probe in colony hybridization assays. Only two strains carried daaE and expressed F1845, suggesting that this fimbria is rare among DAEC strains.     

Incidence and some characteristics of fimbriae FY and 31A of Escherichia coli isolates from calves with diarrhea in Japan

Escherichia coli isolates from calves with diarrhea (1 day to 8 weeks old, 140 individuals) were surveyed for the three immunologically distinct fimbrial adhesins FY, 31A, and K99. Of a total of 1,370 strains isolated, 96 (7.0%), 34 (2.5%), 75 (5.5%), and 13 (0.9%) were identified as FY+, 31A+, FY+.31A+, and K99+, respectively. The K99+ strains also manifested heat-stable enterotoxin production (ST+), while FY+, 31A+, and FY+.31A+ strains were ST-. Expression of FY and 31A was repressed at lower temperatures or poor aeration. The FY+ and 31A+ E. coli showed mannose-resistant hemagglutinating activity with bovine erythrocytes. Electron microscopy revealed that FY is a gently curled fimbria with a mean diameter of 4.2 nm, and 31A is a fimbria with a mean diameter of 5.1 nm. The molecular mass of protein subunits was found to be approximately 20 kilodaltons (Kd) and 19 Kd for FY and 31A, respectively. Lethal diarrhea of neonatal calves was induced by challenge with the combination of a K99+.ST+ E. coli strain and either a 31A+ E. coli strain or a 31A+ E. coli strain plus an FY+ E. coli strain under the experimental conditions in which lethal diarrhea was not induced by challenge with a K99+.ST+ E. coli strain alone.     

Novel cell-binding activity specific for N-acetyl-D-glucosamine in an Escherichia coli strain

Escherichia coli strains isolated from patients with different levels of urinary tract infection and from healthy persons were tested for their ability to haemagglutinate endo-beta-galactosidase-treated human erythrocytes. Among the 104 strains studied one revealed a strong agglutination reaction with the enzyme-treated erythrocytes. From the monosaccharides tested N-acetyl-D-glucosamine inhibited agglutination most effectively. Orosomucoid and asialo-orosomucoid had no effect on the haemagglutination whereas beta-galactosidase treated asialo-orosomucoid was inhibitory. These findings indicate that the E. coli strain studied contains a novel cell-binding activity with specificity for terminal N-acetyl-D-glucosamine residues.     

Molecular characterization of a fimbrial adhesin, F1845, mediating diffuse adherence of diarrhea-associated Escherichia coli to HEp-2 cells.

A fimbrial adhesin, designated F1845, was found to be responsible for the diffuse HEp-2 cell adherence of a diarrheal Escherichia coli isolate. The genetic determinant of F1845 was cloned, and the order of the genes necessary for production of F1845 was determined by maxicell analysis. Five polypeptides with apparent sizes of 10, 95, 27, 15.5, and 14.3 kilodaltons (kDa) were found to be encoded in that order by the F1845 determinant. The nucleotide sequence of the 14.3-kDa subunit gene was determined and found to share extensive homology in its signal sequence with the gene encoding the structural subunit of the AFA-1 hemagglutinin of a uropathogenic E. coli strain (A. Labigne-Roussel, M.A. Schmidt, W. Walz, and S. Falkow, J. Bacteriol. 162:1285-1292, 1985) but not in the region encoding the mature protein. Southern blot hybridizations indicated that the F1845 determinants are of chromosomal origin. Hybridization studies using a probe from the region encoding the 95-kDa polypeptide indicated that related sequences may be plasmid associated in some strains and chromosomal in others. Additional hybridization studies of E. coli isolates possessing sequence homology to the F1845 determinant suggest that the sequences in the 5' region of the F1845 structural subunit gene are more highly conserved than sequences in the 3' region.     

Correlation between the presence of aggregative fibria and a type of Escherichia coli adhesion

Enteroaggregative strains of E. coli (EAEC) are an important agents possessing among many virulence factors, aggregative fimbria AAF hemagglutinating in the presence of mannose human group A or/and rats erythrocytes. The aim of the study was to determine the correlation between the presence of AAF fimbria and pattern of adherence in vitro. Tested strains of E. coli were obtained from children with diarrhea (133 strains) and healthy children (105 strains). Among strains of E. coli from children with diarrhea 81 (61%) showed the presence of AAF fimbria and 19 (23%) were adhering in aggregative pattern. In the group of strains of E. coli isolated from healthy children 31 (30%) were AAF positive and 8 (25.8%) of them presented aggregative adherence. Examination of AAF fimbria only dose not allow to distinguish EAEC strains. The data showed the participation of EAEC strains in diarrhea of children below 3 years old.     

Identification and characterization of a gene cluster mediating enteroaggregative Escherichia coli aggregative adherence fimbria I biogenesis.

The aggregative pattern of adherence (AA) exhibited by enteroaggregative Escherichia coli upon HEp-2 cells is a plasmid-associated property which correlates with aggregative adherence fimbria I (AAF/I) expression and human erythrocyte hemagglutination. By using cloning and mutagenesis strategies, two noncontiguous plasmid segments (designated regions 1 and 2) required for AA expression have previously been identified in enteroaggregative E. coli 17-2. TnphoA mutagenesis was performed on clones containing region 1, and 16 TnphoA mutants which were negative for the AA phenotype were analyzed. The TnphoA insertion site for each mutant was determined by junctional DNA sequencing. All 16 mutations occurred within a 4.6-kb span in region 1. Nucleotide sequence analysis of the region revealed four contiguous open reading frames, designated aggDCBA, in the same span. AA-negative TnphoA insertions into all open reading frames except aggB were obtained. On the basis of mutational analysis and protein homology data, it is inferred that aggA, aggC, and aggD are involved in biogenesis of AAF/I, encoding a major fimbrial subunit, outer membrane usher, and periplasmic fimbrial chaperone, respectively. By immunogold electron microscopy, polyclonal antiserum raised against the aggA gene product decorated AAF/I fimbriae, affirming that AggA encodes an AAF/I subunit.     

Galactosyl-binding lectins from the tunicate Didemnum candidum. Carbohydrate specificity and characterization of the combining site

The plasma of the ascidian Didemnum candidum possesses lectin activity directed toward galactosyl moieties. We report the characterization of the affinity chromatography-purified galactosyl-binding lectins from the plasma of this protochordate species in terms of their hemagglutination patterns, temperature stability, saccharide specificities, divalent cation requirements, and the comparison of the properties of their combining sites to those of other characterized lectins. The major galactosyl-specific lectin, termed DCL-I, has an apparent mass of 14,500 daltons and a minor lectin (DCL-II) has an apparent subunit mass of 15,500 daltons. The two molecules differed somewhat in their hemagglutination profiles with untreated and enzyme-treated erythrocytes: a 10-fold increase in DCL-II concentration is required to obtain agglutination titers comparable to those of DCL-I. Although both DCL-I and DCL-II will agglutinate neuraminidase-treated erythrocytes from all vertebrate species tested and most Pronase-treated erythrocytes, DCL-I will agglutinate some untreated erythrocytes which are not agglutinated by DCL-II. Both lectins required divalent cations, were inactivated by temperatures above 70 degrees C, and both exhibited optimal agglutinating activity over a wide range of pH (from 5 to 11). The DCL-I molecule was characterized for its saccharide specificity by binding and inhibition assays using characterized sugars and glycoproteins. Galactose and oligosaccharides bearing nonreducing terminal galactose were the best inhibitors. The inhibition analysis indicated that the DCL-I combining site is small, interacts only with hydroxyls on carbons 2, 3, and 4 of galactose, and exhibits moderate steric hindrance for voluminous groups on carbon 6 and the alpha-anomeric linkage. The data suggest that the combining site would be smaller than the peanut lectin combining site for galactose since DCL-I does not interact with the subterminal monosaccharide hydroxyls for C4 and C6 as does peanut agglutinin. To our knowledge, this is the first isolation and detailed characterization of a lectin from a protochordate species.     

Production, purification, and luminometric analysis of recombinant Saccharomyces cerevisiae MET3 adenosine triphosphate sulfurylase expressed in Escherichia coli

ATP sulfurylase cDNA from MET3 on chromosome X of Saccharomyces cerevisiae was amplified and cloned, and recombinant ATP sulfurylase was expressed in Escherichia coli. The synthesis of ATP sulfurylase was directed by an expression system that employs the regulatory genes of the luminous bacterium Vibrio fischeri. A soluble, biologically active form was purified to electrophoretic homogeneity from lysates of recombinant E. coli by ammonium sulfate fractionation, ion-exchange chromatography, and gel filtration. The specific activity of the purified enzyme was estimated to 140 U/mg. The apparent molecular mass of the recombinant enzyme was determined by gel filtration to be 470 kDa, which indicates that the active enzyme is an octamer of identical subunits (the molecular mass of a single subunit is 59.3 kDa). The ATP sulfurylase activity was monitored in real time by a very sensitive bioluminometric method.     

Expression in Escherichia coli of BCY1, the regulatory subunit of cyclic AMP-dependent protein kinase from Saccharomyces cerevisiae. Purification and characterization

The regulatory (R) subunit of cAMP-dependent protein kinase from the yeast Saccharomyces cerevisiae was expressed in Escherichia coli by engineering the gene for yeast R, BCY1, into an E. coli expression vector that contained a promoter from phage T7. Oligonucleotide-directed mutagenesis was used to create an NdeI restriction site at the natural ATG of the yeast R. This facilitated construction of the T7 expression vector so that the sequence of the protein produced was identical to the natural R subunit. Yeast R was highly expressed in a soluble form. 20 mg of purified yeast R was obtained from 4 liters of E. coli. N-terminal amino acid sequencing revealed that the expressed protein began with the natural sequence. 60% of the molecules contained an N-terminal methionine, and 40% initiated with valine, the second amino acid of yeast R. The protein produced in E. coli migrated on a sodium dodecyl sulfate-polyacrylamide gel with an Mr of 52,000. The yeast R bound 2 mol of cAMP/mol of R monomer with a Kd of 76 nM. The protein was treated with urea to remove bound cAMP. Sedimentation values before and after the urea treatment were identical (s20,w = 5.1). Addition of purified R subunit to a preparation of yeast C subunit (TPK1) rendered catalytic activity cAMP-dependent with an activity ratio of 4.6. The yeast R was autophosphorylated by yeast C to a level of 0.8 mol of phosphate/mol of R monomer. By these criteria, the R subunit produced in E. coli was structurally and functionally identical to the natural yeast R subunit and similar to mammalian type II R subunits.     

Purification and characterization of recombinant human interleukin-2 produced in Escherichia coli

Recombinant human interleukin-2 (rIL-2) produced in Escherichia coli was purified to apparent homogeneity by cation exchange chromatography and reverse phase high performance liquid chromatography. The amino acid composition, amino terminal amino acid sequence, and carboxyl terminal amino acid were consistent with those deduced from the cDNA sequence. Besides the molecular species with the amino terminal Ala, the purified preparation contained another species having an additional Met residue at the amino terminus corresponding to the initiation codon AUG. The molar absorption coefficient of rIL-2 was determined to be 9.58 X 10(3) M-1 cm-1 at 280nm in water. Ultracentrifugal analyses revealed that it existed as a monomeric form in 0.1 M NaCl. The apparent sedimentation coefficient (S20,w) was calculated to be 1.8 S.     

Functional expression and characterization of a bacterial light-harvesting membrane protein in Escherichia coli and cell-free synthesis systems

Heterologous expression of a bacterial light-harvesting (LH) integral membrane protein was attempted using Escherichia coli cells and cell-free synthesis systems prepared from E. coli extracts. The alpha-apoprotein of LH1 complex from purple photosynthetic bacterium Rhodospirillum rubrum was overexpressed as a recombinant protein with a histidine (His6) tag added to the carboxyl terminus. Both of the expression systems produced alpha-apoprotein in a fully functional form as can judged by its ability to form a structural subunit with native beta-apoprotein and the pigment molecule bacteriochlorophyll a. The expression product in E. coli appears to be located in the inner cell membrane and can be almost completely extracted by 0.5% (w/v) Triton X-100. Circular dichroism measurement indicated that the expressed alpha-apoproteins from both systems had alpha-helical contents essentially identical with that of the native one. About two thirds of the alpha-apoprotein expressed in E. coli was found to have the amino terminal methionine residue modified by a formyl group. About one third of the alpha-apoprotein expressed in the cell-free system was found to be oxidized at the side chain of the amino terminal methionine residue. Functional expression of the alpha-apoprotein using the cell-free system provides an useful example for producing highly hydrophobic integral membrane proteins with relatively large quantities sufficient for biophysical and structural analysis.     

Role of fimbrial adhesins in the pathogenesis of Escherichia coli infections.

Escherichia coli strains are able to cause intestinal (enteritis, diarrhoeal diseases) and extraintestinal (urinary tract infections, sepsis, meningitis) infections. Most pathogenic E. coli strains produce specific fimbrial adhesins, which represent essential colonization factors: intestinal E. coli strains very often carry transferable plasmids with gene clusters specific for fimbrial adhesins, like K88 and K99, or colonization factor antigens (CFA) I and II. In contrast, the fimbrial gene clusters of extraintestinal E. coli strains, such as P, S, or F1C fimbriae, are located on the chromosomes. The fimbrial adhesin complexes consist of major and minor subunit proteins. Their binding specificity can generally be assayed in hemagglutination tests. In the case of fimbrial adhesins of intestinal E. coli strains, the major subunit proteins preferentially represent the hemagglutinating adhesins, whereas minor subunit proteins are the hemagglutinins of extraintestinal E. coli strains. Recently "alternative" adhesin proteins were identified, which have the capacity to bind to eukaryotic structures different from the receptors of the erythrocytes. Fimbrial adhesins are not constitutively expressed but are stringently regulated on the molecular level. Extraintestinal E. coli wild-type strains normally carry three or more fimbrial adhesin determinants, which have the capacity to influence the expression of one another (cross talk). Furthermore the fimbrial gene clusters undergo phase variation, which seems to be important for their contribution to pathogenesis of E. coli.     

EnvC, a new lipoprotein of the cytoplasmic membrane of Escherichia coli

Abstract A gene product with an apparent molecular mass of approximately 39000 Da can be identified in the cytoplasmic membrane of Escherichia coli upon expression of cloned envC . In this communication we report that the product was labelled with [³H]glycerol and [³H]palmitic acid, and a precursor molecule of increased molecular mass was accumulated when cells were treated with globomycin, a specific inhibitor for the prolipoprotein signal peptidase. The same precursor molecule was encoded by an envC mutant gene, in which the cysteine residue in a pentapeptide sequence, Leu-Ile-Ala-Gly-Cys²⁴ within the amino terminal region of EnvC, was replaced by tryptophane (Trp²⁴). This protein was not labelled with [³H]glycerol. The results demonstrate that the envC gene product represents a new lipoprotein of the cytoplasmic membrane of E. coli .     

Expression of native rabbit light meromyosin in Escherichia coli. Observation of a powerful internal translation initiation site

The cDNA-sequence coding for rabbit skeletal muscle light meromyosin (LMM) was placed under the control of the lambda promoter (PL) of an Escherichia coli expression vector. The resulting plasmid pEXLMM74 expressed non-fused rabbit skeletal muscle LMM with yields ranging from 1 to 5% of the total proteins of E. coli. This LMM was specifically recognized by polyclonal antibodies raised against chicken pectoralis muscle myosin. It could be highly enriched from E. coli extracts by using two cycles of high and low ionic strength buffer. The partially purified protein contained a major side-product, with a calculated molecular mass of 59 kilodaltons, that is produced by translation initiation from a site in the coding region of LMM. After deletion of the translation initiation site derived from the expression plasmid, only the 59 kilodalton protein is expressed in E. coli from the resulting plasmid pEXLMM59. Both the 74 and 59 kilodalton proteins were shown to form paracrystals. They were studied by electron microscopy using negative staining and were found to show characteristic striations with an axial periodicity of about 43 nm. By circular dichroism measurement we showed that the purified 59 kilodalton protein is folded mostly as an alpha-helix.     

鲎血细胞中脂多糖结合蛋白TALF在大肠杆菌中的表达研究

TALF(Tachyleus antilipoposaccharide factor)对细菌内毒素（LPS）的核心部分有抑制作用。研究TALF cDNA基因在大肠杆菌中的表达,首先将TALF cDNA基因分别插入大肠杆菌表达载体pGEX-4T-2、pET22b、pET28a中,构建重组表达质粒,转化于大肠杆菌BL21(DE3)。结果表明克隆于pET22b、pET28a中的TALF cDNA基因没有表达,而融合了GST的TALF基因（GST-TALF）能够在大肠杆菌中表达,并形成包涵体。从1L培养基中可获得4mg纯度为91%的GST-TALF融合蛋白。经复性和纯化后的融合蛋白GST-TALF几乎检测不到抑菌活性及LPS中和活性,但该融合蛋白经凝血酶消化后表现出明显的体外抑菌活性及LPS中和活性。     

Cloning, nucleotide sequence, and hybridization studies of the type IIb heat-labile enterotoxin gene of Escherichia coli.

Type IIb heat-labile enterotoxin (LT-IIb) is produced by Escherichia coli 41. Restriction fragments of total cell DNA from strain 41 were cloned into a cosmid vector, and one cosmid clone that encoded LT-IIb was identified. The genes for LT-IIb were subcloned into a variety of plasmids, expressed in minicells, sequenced, and compared with the structural genes for other members of the Vibrio cholerae-E. coli enterotoxin family. The A subunits of these toxins all have similar ADP-ribosyltransferase activity. The A genes of LT-IIa and LT-IIb exhibited 71% DNA sequence homology with each other and 55 to 57% homology with the A genes of cholera toxin (CT) and the type I enterotoxins of E. coli (LTh-I and LTp-I). The A subunits of the heat-labile enterotoxins also have limited homology with other ADP-ribosylating toxins, including pertussis toxin, diphtheria toxin, and Pseudomonas aeruginosa exotoxin A. The B subunits of LT-IIa and LT-IIb differ from each other and from type I enterotoxins in their carbohydrate-binding specificities. The B genes of LT-IIa and LT-IIb were 66% homologous, but neither had significant homology with the B genes of CT, LTh-I, and LTp-I. The A subunit genes for the type I and type II enterotoxins represent distinct branches of an evolutionary tree, and the divergence between the A subunit genes of LT-IIa and LT-IIb is greater than that between CT and LT-I. In contrast, it has not yet been possible to demonstrate an evolutionary relationship between the B subunits of type I and type II heat-labile enterotoxins. Hybridization studies with DNA from independently isolated LT-II producing strains of E. coli also suggested that additional variants of LT-II exist.     

Cloning, characterization, and nucleotide sequence of a gene encoding Microbispora bispora BglB, a thermostable beta-glucosidase expressed in Escherichia coli.

Genomic DNA fragments encoding beta-glucosidase activities of the thermophilic actinomycete Microbispora bispora were cloned into Escherichia coli. Transformants expressing beta-glucosidase activity were selected by their ability to hydrolyze the fluorogenic substrate 4-methylumbelliferyl-beta-D-glucoside. Two genes encoding beta-glucosidase activity were isolated and distinguished by restriction analysis, Southern hybridization, and the substrate specificities of the encoded enzymes. One gene, bglB, encoded a beta-glucosidase that was expressed intracellularly in E. coli. It exhibited a molecular mass of approximately 52,000 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and 51,280 Da by nondenaturing gradient PAGE, a pI of 4.6, and temperature and pH optima of 60 degrees C and 6.2, respectively. Cloned BglB showed greater activity against cellobiose than against aryl-beta-D-glucosides and was thermostable, retaining about 70% of its activity after 48 h at 60 degrees C. BglB activity is activated two- to threefold in the presence of 2 to 5% (0.1 to 0.3 M) glucose. The DNA sequence of the 2.2-kb insert carrying bglB has been determined. An open reading frame which codes for a protein of 473 amino acids with a predicted molecular mass of 52,227 Da showed significant homology (40 to 47% identity) with beta-glucosidases from glycosal hydrolase family 1.     

Cloning, characterization, and nucleotide sequence of a gene encoding Microbispora bispora BglB, a thermostable beta-glucosidase expressed in Escherichia coli.

Genomic DNA fragments encoding beta-glucosidase activities of the thermophilic actinomycete Microbispora bispora were cloned into Escherichia coli. Transformants expressing beta-glucosidase activity were selected by their ability to hydrolyze the fluorogenic substrate 4-methylumbelliferyl-beta-D-glucoside. Two genes encoding beta-glucosidase activity were isolated and distinguished by restriction analysis, Southern hybridization, and the substrate specificities of the encoded enzymes. One gene, bglB, encoded a beta-glucosidase that was expressed intracellularly in E. coli. It exhibited a molecular mass of approximately 52,000 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and 51,280 Da by nondenaturing gradient PAGE, a pI of 4.6, and temperature and pH optima of 60 degrees C and 6.2, respectively. Cloned BglB showed greater activity against cellobiose than against aryl-beta-D-glucosides and was thermostable, retaining about 70% of its activity after 48 h at 60 degrees C. BglB activity is activated two- to threefold in the presence of 2 to 5% (0.1 to 0.3 M) glucose. The DNA sequence of the 2.2-kb insert carrying bglB has been determined. An open reading frame which codes for a protein of 473 amino acids with a predicted molecular mass of 52,227 Da showed significant homology (40 to 47% identity) with beta-glucosidases from glycosal hydrolase family 1.