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  • 1
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A DNA fragment (pCHI5422) containing two genes encoding a 54-kDa and a 22-kDa chitinase was isolated from a cosmid DNA library of Serratia marcescens KCTC2172. The complete nucleotide sequence of pCHI5422 consisting of 4581 bp was determined. The nucleotide sequence of the 22-kDa chitinase consists of 681 bp of open reading frame encoding 227 amino acids and is located 1422 bp downstream of the translation termination codon of the 54-kDa chitinase sequence. The 54-kDa chitinase gene consisted of 1497 bp in a single open reading frame encoding 499 amino acids. The genes encoding the 54-kDa and 22-kDa chitinase were separately subcloned in Escherichia coli and the individual chitinases were expressed and purified from the culture broth using chitin affinity chromatography. When chitohexaose was used as substrate, the major product of the enzymatic reaction of both the 54-kDa and 22-kDa chitinases was a (GlcNAc)2 dimer with a minor amount of monomer. The specific activity of the 54-kDa and 22-kDa chitinases were 300 μM (min)−1 mg−1 and 17 μM (min)−1 mg−1 on the natural swollen chitin, respectively.
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  • 2
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A chitinase gene (pCHI52) encoding the 52-kDa chitinase was isolated from a Serratia marcescens KCTC2172 cosmid library. This chitinase gene consists of 2526 bp with an open reading frame that encodes 485 amino acids. Escherichia coli harboring the pCHI52 gene secreted not only a 52-kDa but also a 35-kDa chitinase into the culture supernatant. We purified both 52-kDa and 35-kDa chitinases using a chitin affinity column and Sephacryl-S-300 gel filtration chromatography. We determined that the 17 N-terminal amino acid sequences of the 52-kDa and the 35-kDa chitinase are identical. Furthermore, a protease obtained from S. marcescens KCTC2172 cleaved the 52-kDa chitinase into the 35-kDa protein with chitinase activity. These results suggest that the 35-kDa chitinase derives from the 52-kDa chitinase by post-translational proteolytic modification. The optimal reaction temperature of 45°C and the optimal pH of 5.5 were identical for both enzymes. The specific activities of the 52-kDa and 35-kDa chitinases on natural swollen chitin were 67 μmol min−1 mg−1 and 60 μmol min−1 mg−1, respectively.
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  • 3
    ISSN: 1432-2048
    Keywords: Key words: Differential display ; Functional analysis ; Fungal elicitor treatment ; Oryza (rab-GDIs) ; Pathogen signaling ; Rab-specific GDP dissociation inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. By using the mRNA differential display approach to isolate defense signaling genes active at the early stage of fungal infection two cDNA fragments with high sequence homology to rab-specific GDP-dissociation inhibitors (GDIs) were identified in rice (Oryza sativa L.) suspension cells. Using polymerase-chain-reaction products as probes, two full-length cDNA clones were isolated from a cDNA library of fungal-elicitor-treated rice, and designated as OsGDI1 and OsGDI2. The deduced amino acid sequences of the isolated cDNAs exhibited substantial homology to Arabidopsis rab-GDIs. Northern analysis revealed that transcripts detected with the 3′-gene-specific DNA probes accumulated to high levels within 30 min after treatment with a fungal elicitor derived from Magnaporthe grisea. The functionality of the OsGDIs was demonstrated by their ability to rescue the Sec19 mutant of Saccharomyces cerevisiae which is defective in vesicle transport. The proteins, expressed in Escherchia coli, cross-reacted with a polyclonal antibody prepared against bovine rab-GDI. Like bovine rab-GDI, the OsGDI proteins efficiently dissociated rab3A from bovine synaptic membranes. Using the two-hybrid system, it was shown that the OsGDIs specifically interact with the small GTP-binding proteins belonging to the rab subfamily. The specific interaction was also demonstrated in vitro by glutathione S-transferase resin pull-down assay.
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  • 4
    ISSN: 1573-5028
    Keywords: complementation ; small GTP-binding protein ; soybean cDNAs ; Ypt/Rab-related genes ; ypt-1 mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have previously reported the isolation of a gene from a soybean cDNA library encoding a Ypt/Rab-related small GTP-binding protein, Sypt. Here, we report the isolation of a second Ypt/Rab-related gene, designated Srab2, from the same soybean cDNA library. And we compare the in vivo function of the two soybean genes utilizing a yeast ypt1-1 mutant. The Srab2 gene encodes 211 amino acid residues with a molecular mass of 23 169 Da. The deduced amino acid sequence of the Srab2 is closely related to the rat (76%) and human (75%) Rab2 proteins, but it shares relatively little homology to Sypt (46%) and Saccharomyces cerevisiae ypt proteins (41%). Genomic Southern blot analysis using the cDNA insert of Srab2 revealed that it belongs to a multigene family in the soybean genome. The protein encoded by Srab2 gene, when expressed in Escherichia coli, disclosed a GTP-binding activity. The expression pattern of the Srab2 gene is quite different from that of the Sypt gene. The Srab2 gene is predominantly expressed in the plumule region, while expression was very low in the other areas in soybean seedlings. On the other hand, the Sypt mRNA is not detectable in any tissues of soybean seedlings grown in the dark. However, light significantly suppressed the Srab2 gene expression, but enhanced the transcript levels of the Sypt gene in leaf and, at even higher levels, in root tissues. When the Srab2 and Sypt genes are introduced separately into a S cerevisiae defective in vesicular transport function, the Srab2 gene cannot complement the temperature-sensitive yeast ypt1-1 mutation at all, in contrast to the Sypt gene. In conclusion, the difference of functional complementation of the yeast mutation together with differential expression of the two genes suggest that the in vivo roles of the Srab2 and Sypt genes may be different in soybean cells.
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  • 5
    ISSN: 1573-5028
    Keywords: ADP-ribosylation ; G protein α subunit ; inclusion body ; rice ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone, RGA1, was isolated by using a GPA1 cDNA clone of Arabidopsis thaliana G protein α subunit as a probe from a rice (Oryza sativa L. IR-36) seedling cDNA library prepared from roots and leaves. Sequence analysis of genomic clone reveals that the RGA1 gene has 14 exons and 13 introns, and encodes a polypeptide of 380 amino acid residues with a calculated molecular weight of 44.5 kDa. The encoded protein exhibits a considerable degree of amino acid sequence similarity to all the other known G protein α subunits. A putative TATA sequence (ATATGA), a potential CAAT box sequence (AGCAATAC), and a cis-acting element, CCACGTGG (ABRE), known to be involved in ABA induction are found in the promoter region. The RGA1 protein contains all the consensus regions of G protein α subunits except the cysteine residue near the C-terminus for ADP-ribosylation by pertussis toxin. The RGA1 polypeptide expressed in Escherichia coli was, however, ADP-ribosylated by 10 μM [adenylate-32P] NAD and activated cholera toxin. Southern analysis indicates that there are no other genes similar to the RGA1 gene in the rice genome. Northern analysis reveals that the RGA1 mRNA is 1.85 kb long and expressed in vegetative tissues, including leaves and roots, and that its expression is regulated by light.
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  • 6
    ISSN: 1573-5028
    Keywords: Brassica Sar1-like cDNAs ; small GTP-binding protein ; suppression ; yeast Sec12-1 mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two new members (Bsar1a and Bsar1b) of the Sar1 gene family have been identified from a flower bud cDNA library of Brassica campestris and their functional characteristics were analyzed. The two clones differ from each other at 14 positions of the 193 amino acid residues deduced from their coding region. The amino acid sequences of Bsar1a and Bsar1b are most closely related to the Sar1 family, genes that function early in the process of vesicle budding from the endoplasmic reticulum (ER). The sequences contain all the conserved motifs of the Ras superfamily (G1–G4 motifs) as well as the distinctive structural feature near the C-terminus that is Sar1 specific. Our phylogenetic analysis confirmed that these two clones can indeed be considered members of the Sar1 family and that they have a close relationship to the ARF family. The Bsar1 proteins, expressed in Escherichia coli, cross-reacted with a polyclonal antibody prepared against Saccharomyces cerevisiae Sar1 protein. It also exhibited GTP-binding activity. Genomic Southern blot analysis, using the 3'-gene-specific regions of the Bsar1 cDNAs as probes, revealed that the two cDNA clones are members of a B. campestris Sar1 family that consists of 2 to 3 genes. RNA blot analysis, using the same gene-specific probes, showed that both genes are expressed with similar patterns in most tissues of the plant, including leaf, stem, root, and flower buds. Furthermore, when we placed the two Bsar1 genes under the control of the yeast pGK1 promoter into the temperature-sensitive mutant yeast strain S. cerevisiae Sec12-1, they suppressed the mutation which consists of a defect in vesicle transport. The amino acid sequence similarity, the GTP-binding activity, and the functional suppression of the yeast mutation suggest that the Bsar1 proteins are functional homologues of the Sar1 protein in S. cerevisiae and that they may perform similar biological functions.
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