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  • General Chemistry  (35)
  • Biochemistry and Biotechnology  (18)
  • gene expression  (6)
  • 1
    ISSN: 1573-5028
    Keywords: acetohydroxyacid synthase ; gene organization ; gene expression ; herbicide resistance ; cotton ; Gossypium hirsutum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The acetohydroxyacid synthase (AHAS) gene family of the cotton AD allotetraploid Gossypium hirsutum has been cloned and characterized. We have identified six different AHAS genes from an analysis of genomic clones and Southern blots of genomic DNA. Four of the six genes are organized as tandem pairs, in which the genes are separated by only 2–3 kb. Conservation of restriction fragment length polymorphisms between G. hirsutum and A-genome and D-genome-containing diploid cottons was sufficient to assign the single genes in clones A5 and A19 to the A and D subgenomes, respectively. Each diploid genome has one tandem pair, but in these cases we could not make specific subgenomic assignments. DNA and deduced amino acid sequences were determined for the A5 and A19 genes, and an AHAS cDNA clone isolated from a leaflibrary. The sequence of the A19 gene matches that of the cDNA clone, while the A5 gene is 97.8% similar. The four genes comprising the tandem pairs are much less similar to the cDNA clone. The deduced amino acid sequences of the mature polypeptides encoded by the A5 and A19 genes are collinear with the housekeeping forms of AHAS from Arabidopsis thaliana, Nicotiana tabacum and Brassica napus. The constitutive expression of A5 and A19 was confirmed with RNase protection assays and northern blots. We conclude that these genes encode the main house-keeping froms of AHAS in G. hirsutum. Among the four AHAS genes comprising the two tandem pairs, at least two are functional. These genes exhibit either low-level constitutive expression (one or both of the ‘downstream’ genes of each pair), or highly specific expression in reproductive tissue (one or both of the ‘upstream’ genes of each pair). The AHAS gene family of G. hirsutum is more complex than that of other plants so far examined.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: C4 photosynthesis ; gene structure ; gene expression ; genetic variation ; silent substitution ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the structure of the maize (Zea mays L. subsp.mays line B73) nuclear gene encoding the phosphoenolpyruvate (PEP) carboxylase isozyme involved in C4 photosynthesis. The gene is 5.3 kb long and has ten exons that range in size from 85 to 999 bp. The nine introns vary from 97 to 872 bp. The sequence of 663 bp of 5′-flanking and 205 bp of 3′-flanking DNA is reported along with the entire gene sequence. Several short repetitive sequences were found in the 5′-flanking DNA that have characteristics similar to elements important in the light regulation of pea genes encoding the small subunit of ribulose 1,5-bisphosphate carboxylase. In addition, some 5′-flanking sequence similarities were found in a comparison with other light-regulated genes from maize and wheat. The level of DNA sequence variation among different PEP carboxylase alleles is similar to the allelic variation observed for several other maize nuclear genes. The data suggest modern maize variaties have retained much of the genetic variation present in their ancestral forms. Finally, accumulation of transcripts encoding the PEP carboxylase isozyme involved in C4 photosynthesis is quite high in several structures besides leaves, including inner leaf sheaths, tassels and husks. This indicates that expression of this gene is not leaf-specific and may not necessarily be coupled to the development of Kranz anatomy.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 19 (1992), S. 959-971 
    ISSN: 1573-5028
    Keywords: gene expression ; gene variants ; pre-mRNA splicing ; pseudogenes ; U1 small nuclear RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract U1 small nuclear RNAs (U1snRNAs) occur in the nucleus of plants and animals where, complexed with several proteins in the form of U1 small nuclear ribonucleoprotein particles (U1snRNPs), they play an important role in precursor messenger RNA (pre-mRNA) splicing. Ten potato U1snRNA genes have been isolated on two genomic clones illustrating the clustering of this multigene family on the potato genome. Based on both the sequence of their coding regions and upstream regulatory elements, seven of the genes are potentially functional. The other three genes were pseudogenes with defective promoter or coding region sequences. Analysis of expression of individual cloned U1snRNA genes in transfected tobacco protoplasts was impossible due to the similarity of U1snRNA sequences in tobacco. However, by marking the coding regions with oligonucleotides or constructing chimaeric genes consisting of a potato U1snRNA promoter region and maize U5snRNA coding region, three of the U1 promoter regions were shown to be transcriptionally active.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5028
    Keywords: cotton ; gene expression ; Gossypium hirsutum ; metallothionein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have characterized cotton (Gossypium hirsutum L.) genes encoding type 1 metallothionein-like proteins that are highly expressed in roots. Little or no expression of these genes was detected in other organs and tissues. The deduced amino acid sequences have a high degree of similarity with type 1 metallothionein-like proteins from other plants, including a central hydrophobic domain flanked by conserved cysteine-rich motifs. The type 1 metallothionein-like genes of cotton are encoded by a small gene family. One gene (MT1-A) was analyzed in detail and found to have three exons which are 52, 83 and 397 bp long, and two introns 130 and 1042 bp in length. Three of the type 1 metallothionein-like genes are organized in a tandom array, and the 5′-flanking regions of these genes share a high degree of sequence similarity. Two of the clustered genes (MT1-A andMT1-B) are expressed at about equal levels in roots and use the same transcription start site. A 640 bp promoter fragment from theMT1-A gene was sufficient to direct expression of beta-glucuronidase (GUS) in transformed cotton roots. The expression was highest near the root tip.
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  • 5
    ISSN: 1573-5028
    Keywords: chitinase ; cotton ; gene expression ; 1,3-β-glucanase ; Gossypium hirsutum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated cDNA clones representing mRNAs encoding chitinase and 1,3-β-glucanase in cotton (Gossypium hirsutum L.) leaves. The chitinase clones were sequenced and found to encode a 28,806 Da protein with 71% amino acid sequence similarity to the SK2 chitinase from potato (Solanum tuberosum). The 1,3-β-glucanase clones encoded a 37,645 Da protein with 57.6% identity to a 1,3-β-glucanase from soybean (Glycine max). Northern blot analyses showed that chitinase mRNA is induced in plants treated with ethaphon or salicylic acid, whereas the levels of 1,3-β-glucanase mRNA are relatively unaffected. Southern blots of cotton genomic DNA and genomic clones indicated chitinase is encoded by a small gene family of which two members, Chi 2;1 and Chi 2;2, were characterized. These genes share 97% sequence identity in their transcribed regions. The genes were found to have three exons which are 309, 154 and 550 bp long, and two introns 99 and 154 bp in length. The 5′-flanking regions of Chi 2;1 and Chi 2;2 exhibit a large degree of similarity and may contain sequences important for gene response to chemical agents and fungal attack.
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  • 6
    ISSN: 1573-5028
    Keywords: gene expression ; heterologous expression ; H+/hexose symporter ; Lycopersicon esculentum ; quantitative PCR ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length (LeHT2) and two partial (LeHT1 and LeHT3) cDNA clones, encoding hexose transporters, were isolated from tomato (Lycopersicon esculentum) fruit and flower cDNA libraries. Southern blot analysis confirmed the presence of a gene family of hexose transporters in tomato consisting of at least three members. The full-length cDNA (LeHT2) encodes a protein of 523 amino acids, with a calculated molecular mass of 57.6 kDa. The predicted protein has 12 putative membrane-spanning domains and belongs to the Major Facilitator Superfamily of membrane carriers. The three clones encode polypeptides that are homologous to other plant monosaccharide transporters and contain conserved amino acid motifs characteristic of this superfamily. Expression of the three genes in different organs of tomato was investigated by quantitative PCR. LeHT1 and LeHT3 are expressed predominantly in sink tissues, with both genes showing highest expression in young fruit and root tips. LeHT2 is expressed at relatively high levels in source leaves and certain sink tissues such as flowers. LeHT2 was functionally expressed in a hexose transport-deficient mutant (RE700A) of Saccharomyces cerevisiae. LeHT2-dependent transport of glucose in RE700A exhibited properties consistent with the operation of an energy-coupled transporter and probably a H+/hexose symporter. The K m of the symporter for glucose is 45 μM.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 1-9 
    ISSN: 0887-3585
    Keywords: protein engineering ; cassette mutagenesis ; peptide hormone ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: By inserting appropriate peptide ligands into surface loops on globular proteins, we expect to develop probes for the location, accessibility, and steric and electrostatic environment of these ligand-binding sites on their membrane-bound receptors. Three residues in a loop on the surface of E. coli alkaline phosphatase were substituted by an 18-residue peptide containing the receptor-binding segment of somatostatin-14 without significantly affecting the catalytic properties of the enzyme. This hybrid protein was then used to investigate the ligand-binding site of somatostatin receptors. Tryptic cleavage of the hybrid protein within the inserted sequence, and binding of the hybrid protein to antisomatostatin antibodies demonstrated the surface accessibility of the guest peptide. Both the wild-type enzyme and the hormone-enzyme hybrid displaced 125I-labeled somatostatin from rat brain membrane receptors only at high concentrations. How-ever, chemical cationization of the hybrid protein, which again did not disturb the phosphatase activity, enhanced its receptor-binding potency to a level only 23 times lower than that of somatostatin itself and 280 times higher than that of the cationized wild-type protein. This alkaline phosphatase/somatostatin hybrid protein appears, therefore, to be a suitable starting point for the development of probes for the steric and electrostatic environment of the ligand-binding site of somatostatin receptors. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0887-3585
    Keywords: conformational change ; free energy calculations ; HIV protease ; molecular dynamics simulations ; protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two different structures of ligand-free HIV protease have been determined by X-ray crystallography. These structures differ in the position of two 12 residue, β-hairpin regions (or “flaps”) which cap the active site. The movements of the flaps must be involved in the binding of substrates since, in either conformation, the flaps block the binding site. One of these structures is similar to structures of the ligand-bound enzyme; however, the importance of both structures to enzyme function is unclear. This transformation takes place on a time scale too long for conventional molecular dynamics simulations, so the process was studied by first identifying a reaction path between the two structures and then calculating the free energy along this path using umbrella sampling. For the ligand-free enzyme, it is found that the two structures are nearly equally stable, with the ligand-bound-type structure being less stable, consistent with X-ray crystallography data. The more stable open structure does not have a lower potential energy, but is stabilized by entropy. The transition occurs through a collapse and reformation of the β-sheet structure of the conformationally flexible, glycine-rich flap ends. Additionally, some problems in studying conformational changes in proteins through the use of a single reaction path are addressed. Proteins 32:7-16, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 9 (1991), S. 120-134 
    ISSN: 0887-3585
    Keywords: plasmid SSBs ; protein and DNA sequence ; single-stranded DNA binding proteins ; helix destabilizing proteins ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The DNA and protein sequences of single-stranded DNA binding proteins (SSBs) encoded by the plP71a, plP231a, and R64 conjugative plasmids have been determined and compared to Escherichia coli SSB and the SSB encoded by F-plasmid. Although the amino acid sequences of all of these proteins are highly conserved within the NH2-terminal two-thirds of the protein, they diverge in the COOH-terminal third region. A number of amino acid residues which have previously been implicated as being either directly or indirectly involved in DNA binding are conserved in all of these SSBs. These residues include Trp-40, Trp-54, Trp-88, His-55, and Phe-60. On the basis of these sequence comparisons and DNA binding studies, a role for Tyr-70 in DNA binding is suggested for the first time. Although the COOH-terminal third of these proteins diverges more than their NH2-terminal regions, the COOH-terminal five amino acid residues of all five of these proteins are identical. In addition, all of these proteins share the characteristic property of having a protease resistant, NH2-terminal core and an acidic COOH-terminal region. Despite the high degree of sequence homology among the plasmid SSB proteins, the F-plasmid SSB appears unique in that it was the only SSB tested that neither bound well to poly(dA) nor was able to stimulate DNA polymerase III holoenzyme elongation rates. Poly [d(A-T)] melting studies suggest that at least three of the plasmid encoded SSBs are better helix-destabilizing proteins than is the E. coli SSB protein.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 7 (1965), S. 471-490 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth of Thiobacillus Thiooxidans, utilizing sulfur in three media, was studied by observing changes in halfcell emf, bacterial cell count, and acid production, all as a function of time. A comparison of the biological halfcell emf with comparable control halfcells reveals that T. thiooxidans makes an electrochemical contribution to halfcell voltage. A change from the more complex medium of Skerman's mineral salts to ATCC allowed a clearer delineation of the ability of T. thiooxidans to make an electrochemical contribution. Reproducible biological halfcell emf's were obtained when the ferrous sulfate was removed from the ATCC medium. One halfcell, consisting of T. thiooxidans utilizing sulfur in ATCC, was observed over a 111-day period. During this time, the initial halfcell voltage of -0.35 V. decreased to a value of -0.64 V. (hydrogen emf series). T. thiooxidans, in utilizing sulfur, produces only sulfate ion, thereby simplifying the identification of an electrochemical contribution during growth.
    Additional Material: 12 Ill.
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