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N Y Nguyen

Publications and source records attributed to N Y Nguyen.

16 recordsLinked to original sources
PubMed1992

Isolation, cDNA cloning, and characterization of an 18-kDa hemagglutinin and amebocyte aggregation factor from Limulus polyphemus.

An 18-kDa hemagglutinin which possesses the property of inducing both aggregation of amebocytes and agglutination of erythrocytes has been isolated from Limulus polyphemus amebocytes and purified by ion exchange chromatography. This nonglycosylated, single chain polypeptide with an M(r) of 18,506 and isoelectric point of 8.3 is stored exclusively in the large secretory granules of amebocytes. Based on the partial N-terminal amino acid sequence of 63 residues, DNA probes have been synthesized for screening a pBR322 cDNA library constructed from Limulus amebocytes. The cDNA coding for this protein reveals the presence of a 19-residue signal peptide preceding the 153-residue open reading frame. Northern blot analysis indicates the presence of a single mRNA species. The primary structure derived from the corresponding cDNA sequence reveals an internal homology consisting of two consensus sequences, Val-Asn-Asp/Ser-Trp-Asp and Glu-Asp-Arg-Arg-Trp. The formation of 5 disulfide bonds between 10 half-cysteines divides the molecule into three looped domains each containing the Glu-Asp-Arg-Arg-Trp repeating unit. One of the novel features of this protein is that it shares 37% identity with a 22-kDa mammalian extracellular matrix protein isolated from fetal bovine skin (Neame, P.J., Choi, H.U., and Rosenberg, L.C. (1989) J. Biol. Chem. 264, 5474-5479). The two proteins exhibit a similar pattern of looped domains, each domain containing a homologous consensus sequence (i.e. Glu-Asp-Arg-Arg-Trp). The overall structure of both proteins seems to be highly related, with the exception of an N-terminal tyrosine-rich region present only in the mammalian extracellular matrix protein. The functional properties of the two proteins are similar in that the Limulus 18-kDa protein agglutinates horse erythrocytes and aggregates Limulus amebocytes, and the mammalian 22-kDa protein is an effective adhesion promoter for dermal fibroblasts. On the basis of these unique properties, the newly characterized hemagglutinin has been termed Limulus 18K agglutination-aggregation factor (18K-LAF).

Amino Acid Sequence↗
PubMed1992

Purification and characterization of multiple components of human lymphoblastoid interferon-alpha.

Twenty-two components of human interferon-alpha (IFN-alpha) derived from Sendai virus-induced Namalwa cells were purified by sequential immunoadsorbent affinity chromatography using four monoclonal antibody affinity columns followed by ultrafiltration and reversed-phase high-performance liquid chromatography. The specific activity ranged from 0.2 to 2.6 x 10(8) IU/mg protein on Madin-Darby bovine kidney cells, 0.3 to 4.6 x 10(8) IU/mg protein on human WISH cells, and 10(4) to 7 x 10(5) units/mg protein on mouse L929 cells. The apparent molecular weights of the components ranged from 17,500 to 23,300 using nonreducing sodium dodecyl polyacrylamide-gel electrophoresis and 17,500 to 27,600 using reducing sodium dodecyl polyacrylamide-gel electrophoresis. The amino-terminal amino acid sequences were similar among the components as well as to those reported for the cloned human IFN-alpha genes (Pestka, S. (1986) Methods Enzymol. 119, 3-14). However, four components, f, i, l, and m, have amino-terminal amino acid sequences which appear to be unique when compared to those predicted from the cDNA clones. One component, pre-a, has a potential N-linked glycosylation site on the Asn of residues 2 through 4, Asn-Leu-Ser.

Amino Acid Sequence↗
PubMed1992

Sucrose fermentation by Fusobacterium mortiferum ATCC 25557: transport, catabolism, and products.

Studies of sucrose utilization by Fusobacterium mortiferum ATCC 25557 have provided the first definitive evidence for phosphoenolpyruvate-dependent sugar:phosphotransferase activity in the family Bacteroidaceae. The phosphoenolpyruvate-dependent sucrose:phosphotransferase system and the two enzymes required for the dissimilation of sucrose 6-phosphate are induced specifically by growth of F. mortiferum on the disaccharide. Monomeric sucrose 6-phosphate hydrolase (M(r), 52,000) and a dimeric ATP-dependent fructokinase (subunit M(r), 32,000) have been purified to electrophoretic homogeneity. The physicochemical and catalytic properties of these enzymes have been examined, and the N-terminal amino acid sequences for both proteins are reported. The characteristics of sucrose 6-phosphate hydrolase and fructokinase from F. mortiferum are compared with the same enzymes from both gram-positive and gram-negative species. Butyric, acetic, and D-lactic acids are the end products of sucrose fermentation by F. mortiferum. A pathway is proposed for the translocation, phosphorylation, and metabolism of sucrose by this anaerobic pathogen.

Acetates↗
PubMed1991

Transposon-encoded sucrose metabolism in Lactococcus lactis. Purification of sucrose-6-phosphate hydrolase and genetic linkage to N5-(L-1-carboxyethyl)-L-ornithine synthase in strain K1.

Sucrose-6-phosphate hydrolase from Lactococcus lactis subsp. lactis K1-23 (formerly Streptococcus lactis K1-23) has been purified 600-fold to electrophoretic homogeneity. Purification of the enzyme was achieved by DEAE-Sephacel, phosphocellulose P-11, and gel exclusion (Ultrogel AcA 54) chromatography. The purified enzyme (specific activity 31 units/mg) catalyzed the hydrolysis of both 6-O-phosphoryl-alpha-D-glucopyranosyl-1,2-beta-D-fructofuranoside (sucrose 6-phosphate) and sucrose (Km = 0.1 and 100 mM, respectively). Ultracentrifugal analysis of sucrose-6-phosphate hydrolase indicated an Mr = 52,200. The purified enzyme migrated as a single protein during sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Mr = 52,000). However, four distinct polypeptides were detected by analytical electrofocusing, and all four species hydrolyzed sucrose and sucrose 6-phosphate. The amino acid composition of sucrose-6-phosphate hydrolase, and the sequence of the first 12 amino acids from the NH2 terminus, have been determined. Hybridization studies with oligonucleotide probes show that the genes for sucrose-6-phosphate hydrolase (scrB), Enzyme IIScr of the phosphoenolypyruvate-dependent sucrose:phosphotransferase system (scrA), and N5-(carboxyethyl)ornithine synthase (ceo) are encoded by the same approximately 20-kilobase EcoRI fragment. This fragment is part of a large transposon Tn5306 that also encodes the nisin precursor gene, spaN, and IS904. In L. lactis ATCC 11454, spaN, IS904, scrA, and scrB (but not ceo) are encoded on a related transposon, Tn5307.

Amino Acid Oxidoreductases↗
PubMed1991

Cloning and sequencing of the structural gene for the porin protein of Bordetella pertussis.

Bordetella pertussis produces a porin protein which is a prominent outer membrane component found in both virulent and avirulent strains. N-terminal amino acid analysis of purified B. pertussis porin was performed and this amino acid sequence was used to design an oligonucleotide that was then utilized to screen a lambda gt11 library containing randomly sheared fragments of DNA from B. pertussis strain 347. One clone, lambda BpPor, was identified and subcloned into pUC18. A portion of the DNA insert in this subclone, pBpPor1, was sequenced and shown to contain the N-terminal region of the structural porin gene. This truncated gene sequence was used to design an additional oligonucleotide that was used to identify a clone, pBpPor2, which overlapped with pBpPor1 and contained a termination codon. The structural gene deduced from this sequence would encode a 365-amino-acid polypeptide with a predicted mass of 39,103 daltons. The predicted product also contains a signal sequence of 20 residues that is similar to that found in other porin genes. The predicted B. pertussis porin protein sequence contains regions that are homologous to regions found in porins expressed by Neisseria species and Escherichia coli, including the presence of phenylalanine as the carboxy-terminal amino acid. DNA hybridization studies indicated that both virulent and avirulent strains of B. pertussis contain only one copy of this gene and that Bordetella bronchiseptica and Bordetella parapertussis contain a similar gene.

Amino Acid Sequence↗
PubMed1979

A three-step method for isolating a few to several hundred milligrams of protein.

An operationally simple general protein isolation method was devised from three previously available separation tools, and was tested by application to two demanding fractionation problems and for yield. One test system was the isolation by gel electrofocusing of two model proteins with pI values of 4.6 and 4.8, bovine serum albumin and ovalbumin, with a load of 220 mg each. The other test was the isolation of 10 mg of human growth hormone isohormone B from a mixture of closely migrating other isohormones. The three-step procedure comprises of: (1) separation into zones of homogeneous protein by gel electrofocusing; (2) excision of the zones of homogeneous protein from the gel followed by concentration of the protein to a small volume of solution by means of Steady-State Stacking; (3) purification from polyacrylamide-like contaminants and non-volatile buffers by gel filtration followed by lyophilization. The average overall recovery was 70--80%.

Electrophoresis, Polyacrylamide Gel↗