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  • 1
    Electronic Resource
    Electronic Resource
    A β-lactamase produced by a thermophilic Bacillus (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 140 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A β-lactamase was purified from a thermophilic Bacillus strain, that had been isolated from a traditional hot bath in the Meknes area (Morocco). The properties of the enzyme were very similar to those of the β-lactamase produced by Bacillus licheniformis 749C but it exhibited a somewhat increased thermostability and a higher activation energy with cefazolin as substrate. These properties were expected for an enzyme produced by a thermophilic strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08315.x
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  • 2
    Electronic Resource
    Electronic Resource
    The rate-limiting step in the folding of the cis-Pro167Thr mutant of TEM-1 β-lactamase is the trans to cis isomerization of a non-proline peptide bond (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 104-111 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; guanidine hydrochloride denaturation ; folding/unfolding kinetics ; cis-trans isomerization ; cis-proline mutant ; cis-non-proline amino acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The stability and kinetics of unfolding and refolding of the P167T mutant of the TEM-1 β-lactamase have been investigated as a function of guanidine hydrochloride concentration. The activity of the mutant enzyme was not significantly modified, which strongly suggests that the Glu166-Thr167 peptide bond, like the Glu166-Pro167, is cis. The mutation, however, led to a significant decrease in the stability of the native state relative to both the thermodynamically stable intermediate and the fully unfolded state of the protein. In contrast to the two slower phases seen in the refolding of the wild-type enzyme, only one phase was detected in the refolding of the mutant, indicating a determining role of proline 167 in the kinetics of folding of the wild-type enzyme. The former phases are replaced by rapid refolding when the enzyme is unfolded for short periods of time, but the latter is independent of the time of unfolding. The monophasic refolding reaction of the mutant is proposed to reflect mainly the trans→cis isomerization of the Glu166-Thr167 peptide bond. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.8
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of the folding pathway of the TEM-1 β-lactamase (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 22 (1995), S. 110-118 
    Details
    ISSN: 0887-3585
    Keywords: protein folding ; guanidine hydrochloride denaturation ; molten globule ; folding/unfolding kinetics ; proline isomerization ; slow-folding forms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The TEM-1 β-lactamase is a globular protein containing 12 proline residues. The folding mechanism of this enzyme was investigated by kinetic and equilibrium experiments with the help of fluorescence spectroscopy and circular dichroism. The equilibrium denaturation of the protein induced by guanidine hydrochloride occurs in two discrete steps, indicating the existence of a thermodynamically stable intermediate state. Thisstate is 5.2 ± 0.4 kcal/mol less stable than the native conformation and 5.7 ± 0.2 kcal/mol more stable than the fully denaturedprotein. This intermediate state exhibits a high content of native secondary structure elements but is devoid of specific tertiary organization; its relation to the “molten globule” is discussed. Refolding kinetic experimentsrevealed the existence of a transient intermediate conformation between thethermodynamically stable intermediate and the native protein. This transient intermediate appears rapidly during the folding reaction. It exhibits a secondary structure content very similar to that of the native protein and has also recovered a significant amount of tertiary organisation. The final refolding step of the TEM-1 β-lactamase, leading to the native enzyme, is dominated by two major slow kinetic phases which probablyreflect a very complex process kinetically limited by proline cis/transisomerization. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340220204
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  • 4
    Electronic Resource
    Electronic Resource
    Thiolester substrates of dd-peptidases and β-lactamases (1995)
    Springer
    International journal of peptide research and therapeutics 2 (1995), S. 212-216 
    Details
    ISSN: 1573-3904
    Keywords: dd-Peptidases ; β-Lactamases ; Thiolesters ; Stereospecificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary With peptide substrates, the penicillin-sensitive dd-peptidases exhibit a strict specificity for d-Ala-d-Xaa C-termini. Only glycine is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes also hydrolyse various ester and thiolester analogues of their natural substrates. Some of the thiolesters whose C-terminal leaving group exhibited an l stereochemistry were significantly hydrolysed by some of the studied enzymes, particularly by the Actinomadura R39 dd-peptidase. By contrast, the strict specificity for a d residue in the penultimate position was fully retained. The same esters and thiolesters also behaved as substrates for β-lactamases. In this case, thiolesters exhibiting l stereochemistry in the C-terminal position could also be hydrolysed, mainly by the class C and class D enzymes. But, more surprisingly, the class C Enterobacter cloacae P99 β-lactamase also hydrolysed thiolesters containing an l residue in the penultimate position, sometimes more efficiently than the d isomer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119156
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