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  • 1
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1 = ∼3.3 × 10-4 s-1; B→C, k2 = ∼0.8 × 10-4 s-1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1=∼3.3×10−4s−1; B→C, k2=∼0.8×10−4s−1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 205 (1986), S. 501-506 
    ISSN: 1617-4623
    Keywords: Signal sequence ; Antigenic epitopes ; Outer membrane protein ; Immunogenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Fusion proteins comprising the amino-terminal 99 amino acids of the bacteriophage MS2 replicase and various portions of OmpV a major outer membrane protein of Vibrio cholerae were expressed in Escherichia coli K12. These fusions were expressed under the control of the PL promoter of bacteriophage λ, and expression was controlled using a cIts repressor. Fusions occurring within the secretory signal sequence of OmpV gave rise to the production of mature OmpV. The efficiency, however, decreased with progressive deletion of the signal sequence within the fusions. The reactivity of various OmpV fusions with antisera raised against purified OmpV and whole bacteria demonstrated the existence of two antigenic domains: one present in the denatured form and another in the membrane-associated form of OmpV. These domains correspond to markedly hydrophilic regions of the protein as would be predicted for surface-exposed epitopes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 205 (1986), S. 494-500 
    ISSN: 1617-4623
    Keywords: Signal sequence ; Gene regulation ; Export ; Codon usage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of the ompV gene of Vibrio cholerae was determined. The product of the gene is a 28,000 dalton protein which, after the removal of a 19 amino acid signal sequence, produces a mature outer membrane protein of 26,000 daltons. The cleavage site was determined by amino-terminal amino acid sequencing of the purified mature protein. The DNA upstream of the gene shows the presence of a typical promoter region as judged from the Escherichia coli consensus information; however, the Shine-Dalgarno sequence is associated with a region capable of forming a secondary structure in the mRNA. The formation of this structure would inhibit binding of the mRNA to the ribosome and reduce translation. It is proposed that this structure is recognized by a positive activator in V. cholerae and because of its absence in E. coli ompV is poorly expressed. The distribution of rare codons within ompV suggests that they may serve to slow down the translation of particular domains such that the nascent polypeptide has an opportunity to take up its conformation without interference from the later formed regions. Such a mechanism could aid localization of the protein if export were by a cotranslational secretion system.
    Type of Medium: Electronic Resource
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