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  • 1
    ISSN: 1432-1017
    Keywords: Key words Glutamate dehydrogenase ; Analytical ultracentrifugation ; Allostery ; Quaternary structure ; Subunit communication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract X-ray crystallographic studies have previously shown that glutamate dehydrogenase from Clostridium symbiosum is a homohexamer. Mutation of the active-site aspartate-165 to histidine causes an alteration in the structural properties of the enzyme. The mutant enzyme, D165H exists predominantly as a single species of lower molecular mass than the wild-type enzyme as indicated by gel filtration and sedimentation velocity analysis. The latter technique gives an s20,w value for D165H of (6.07 ± 0.01)S which compares with (11.08 ± 0.01)S for the wild-type, indicative of alteration of the homohexameric quaternary structure of the native enzyme to a dimeric form, a result confirmed by sedimentation equilibrium experiments. Further support for this is provided by chemical modification by Ellman's reagent of cysteine-144 in the mutant, a residue which is buried at the dimer-dimer interface in the wild-type enzyme and is normally inaccessible to modification. The results suggest a possible structural route for communication between the active sites and subunit interfaces which may be important for relaying signals between subunits in allosteric regulation of the enzyme.
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  • 2
    ISSN: 1432-1211
    Keywords: Key words Surface molecule ; Leukocyte ; Immunoglobulin superfamily ; CD84 ; Chromosome 1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  CD84 is a member of the immunoglobulin gene superfamily (IgSF) with two Ig-like domains expressed primarily on B lymphocytes and macrophages. Here we describe the cloning of the mouse homologue of human CD84. Mouse CD84 cDNA clones were isolated from a macrophage library. The nucleotide sequence of mouse CD84 was shown to include an open reading frame encoding a putative 329 amino acid protein composed of a 21 amino acid leader peptide, two extracellular immunoglobulin (Ig)-like domains, a hydrophobic transmembrane region, and an 87 amino acid cytoplasmic domain. Mouse CD84 shares 57.3% amino acid sequence identity (88.7%, considering conservative amino acid substitutions) with the human homologue. Chromosome localization studies mapped the mouse CD84 gene to distal chromosome 1 adjacent to the gene for Ly-9, placing it close to the region where other members of the CD2 IgSF (CD48 and 2B4) have been mapped. Northern blot analysis revealed that the expression of mouse CD84 was predominantly restricted to hematopoietic tissues. Two species of mRNA of 3.6 kilobases (kb) and 1.5 kb were observed. The finding that the pattern of expression was restricted to the hematopoietic system and the conserved sequence of the mouse CD84 homologue suggests that the function of the CD84 glycoprotein may be similar in humans and mice.
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  • 3
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The NAD(P)-dependent glutamate dehydrogenase from Pyrococcus furiosus has been crystallized by the hanging-drop method of vapour diffusion using lithium sulfate as the precipitant. The crystals belong to the tetragonal system and are in space group P42212 with unit-cell dimensions of a = b = 167.2, c = 172.9 Å. Consideration of the values of Vm and possible packing of the molecules within the cell suggest that the asymmetric unit contains a trimer. P. furiosus belongs to the family of Archaea and is one of the most thermostable organisms known, having an optimal growth temperature of 376 K. The glutamate dehydrogenase isolated from this organism has a half-life of 12 h at 373 K and, therefore, the determination of the structure of this enzyme will be important in advancing our understanding of how proteins are adapted to enable them to survive at such extreme temperatures.
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  • 4
    ISSN: 1572-9001
    Keywords: HIDA ; radiopharmaceutical ligand ; monomethyl ester ; impurity ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple procedure for synthesis of HIDA (2,6-dimethylphenylcarbamoylmethyl iminodiacetic acid) is described. It was obtained in better yield by reaction of 2,6-dimethylphenylcarbamoylmethyl chloride with iminodiacetic acid in carbon tetrachloride. The HIDA (A) was identified by IR and1H NMR spectroscopy. Two types of crystals were detected in the crystal final product. Since they could be separated, the crystals:A andB were investigated by X-ray analysis. Crystal and molecular structures were solved by direct methods and refined by full-matrix least-squares technique toR=0.047 andR=0.056, respectively. In the structure ofA, the N2 atom is protonated and the molecule exists as a zwitterion. The crystal structure of compoundA is stabilized by strong hydrogen bonds, which are reflected in higher close-packing coefficient, density, and melting point, compared to compoundB. CompoundB is a monomethyl ester of HIDA, which is present as an impurity in the final recrystallized product.
    Type of Medium: Electronic Resource
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