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  • 1
    Unknown
    Tokyo : Springer
    Keywords: Life sciences ; Human Genetics ; Gene Expression ; Biochemistry ; Cytology ; Life sciences ; Biochemistry, general ; Cell Biology ; Human Genetics ; Gene Expression ; Springer eBooks
    Abstract: This book highlights a new paradigm of translation control by regulatory nascent polypeptides, which is integrated into cellular regulatory systems. Translation lies in the hub of the central dogma of biology, in which the genetic information in the forms of 4-letter sentences is translated into 20-letter sentences: sequences of amino acids that constitute proteins, the functional molecules of life. The process involves a huge number of chemical reactions as well as physical movements of the ribosome along a messenger RNA and takes, on average, tens of seconds in prokaryotes and a few minutes in eukaryotes. Detailed knowledge about the progression of translation, called "elongation", only recently started to accumulate. Newly synthesized and growing polypeptides, called nascent polypeptides, can interact with the intra-ribosomal conduit, called the ribosomal exit tunnel, when they have some specific amino acid sequences, called "an arrest sequence". Such interaction leads to a halt in the elongation reaction. Resulting stalling of the ribosome on messenger RNA can affect the secondary structure and/or localization of the message in the cell, consequently leading to biological outputs such as elevation or reduction of a gene product. This book provides a first collection of knowledge focused on regulatory nascent polypeptides, which have been studied recently using diverse organisms including bacteria, plants, and animals. Readers will be impressed by a new paradigm showing that proteins can function even during the course of their biosynthesis and that the ribosome, the "factory" of protein production, interacts with and inspects its products to adjust the speed of completion of each product. Moreover, regulatory nascent polypeptides can sense or monitor physiological states of the cell and modulate its ability to arrest translation. Living organisms use such intricate control mechanisms of translational speed to regulate gene expression. This book will be a useful addition for established scientists while inspiring students and young scientists to gain deeper insights into the processes of expression of genetic information
    Pages: IX, 315 p. 75 illus., 62 illus. in color. : online resource.
    ISBN: 9784431550525
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: As an approach for studying how SecY, an integral membrane protein translocation factor of Escherichia coli, interacts with other protein molecules, we isolated a dominant negative mutation, secY-d1, of the gene carried on a plasmid. The mutant plasmid severely inhibited export of maltose-binding protein and less severely of OmpA, when introduced into sec+ cells. It inhibited growth of secY and secE mutant cells, but not of secA and secD mutant cells or wild-type cells. The mutation deletes three amino acids that should be located at the interface of cytopiasmic domain 5 and transmembrane segment 9. We also found that some SecY-PhoA fusion proteins that lacked carboxy-terminal portions of SecY but retain a region from periplasmic domain 3 to transmembrane segment 7 were inhibitory to protein export. We suggest that these SecY variants are severely defective in catalytic function of SecY, which requires cytoplasmic domain 5 and its carboxy-terminal side, but retain the ability to associate with other molecules of the protein export machinery, which requires the central portion of SecY; they probably exert the ‘dominant negative’ effects by competing with normal SecY for the formation of active Sec complex. These observations should provide a basis for further genetic analysis of the Sec protein complex in the membrane.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The trpS5 mutation (a mutation in the structural gene for tryptophanyl-tRNA synthetase (TRSase) in E. coli), when present in the genetic background of strain KY913 (HfrH), results in the failure to grow at high temperature (42° C) in a complete medium. The rel (RC relaxed) marker present in this strain was found to be partly responsible for this temperature sensitivity. TRSase in such a strain was rapidly inactivated during growth at 42° C in rich media, but not in minimal media or in the presence of chloramphenicol. A partial derepression of anthranilate synthetase formation took place in the presence of excess tryptophan at growth-restricting temperatures. When some of the trpR mutations (including amber mutations) were combined with trpS5, the resulting double mutants (trpR trpS5) were temperature-insensitive, and TRSase was not inactivated at high temperature, in contrast to the trpR +trpS5 strain. This effect of trpR mutations on temperature sensivity was shown not to be a secondary consequence of the constitutive expression of the trp operon. These findings suggest that the trpR + product interacts with the TRSase of the trpS5 mutant so as to bring about the growth-dependent inactivation of the enzyme. Furthermore, a special class of trpR mutants was obtained whose constitutivity with respect to the trp operon is manifested only in strains carrying trpS5 (but not trpS +) grown at high temperatures. It is proposed that TRSase participates in repression trrough direct interaction with the product of the trpR gene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In an effort to elucidate the control of synthesis of the DNA-dependent RNA polymerase in Escherichia coli, intracellular amounts of the individual subunits were determined by polyacrylamide gel electrophoresis of cell lysates and of precipitates formed with specific antibody against holoenzyme I. Polyacrylamide gel electrophoresis of cell lysates in the presence of sodium dodecyl sulfate has been believed to separate the two larger subunits, β and β′, of RNA polymerase from the bulk of protein in E. coli. However, a polypeptide unrelated to the polymerase was found to migrate in the immediate vicinity of the β′ subunit, interfering with the accurate measurement of this subunit. Taking account of the presence of this peptide, designated tentatively as χ, the quantity of RNA polymerase was estimated relying only on the β subunit. Subunits content was also measured by polyacrylamide gel electrophoresis of the precipitates formed by treating cell lysates with anti-holoenzyme I serum. Since the isolated individual subunits as well as the holo- and core enzyme could be precipitated by the antibody, the present procedure permitted to determine total amounts of the subunits within cells. The subunits α, β and β′, the constituents of core portion of RNA polymerase, were found to be produced coordinately during steady-state growth at different rates within the range examined (0.22 to 1.87 generations/hr) and to be metabolically as stable as the bulk of protein. The rate of synthesis of these subunits relative to the total protein was found to be balanced with the growth rate; the differential rate of synthesis of enzyme core (αp) can be represented by the following empirical equation: αp(%) = 0.7 μ + 0.45, where μ represents growth rate (generation/hr). In contrast, the content of σ subunit was considerably small, i.e. only about one third mole equivalent to enzyme core, and was almost unaffected by the rate of growth.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Keywords: RNA polymerase ; Sigma factor ; Mini-F ; Heat-shock ; DNA replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Escherichia coli htpR (=hin, rpoH) mutants are defective in the induction of heat-shock proteins due to a deficiency in sigma 32 and are unable to grow at high temperature. We found that these mutants are also defective in supporting replication of certain plasmids including F and mini-F. When a htpR mutation is introduced into an F′ strain, the F′ plasmid is effectively excluded. Similarly, when an F′ or mini-F plasmid is introduced into htpR mutant cells, transconjugant or transformant clones are obtained at low frequencies and the plasmid is rapidly lost upon subsequent growth in a non-selective medium. In htpR amber mutants carrying a temperature-sensitive suppressor, mini-F replication occurs normally at 30° C, but is inhibited upon transfer to 40° C where the suppressor tRNA is inactivated. A temperature-resistant “pseudo-revertant” of the htpR6 (amber) mutant, that exhibits apparently normal induction of the major heat-shock proteins in the absence of functional sigma 32, fails to support mini-F replication at 40° C, suggesting that inhibition of mini-F replication is not a secondary consequence of the defective induction of the major heat-shock proteins. It is proposed that the function of the sigma 32 protein is directly required for F plasmid replication.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1617-4623
    Keywords: Protein secretion ; Suppressor of secY ; Riboflavin biosynthesis ; nusB gene ; ssyB mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Escherichia coli gene ssyB was cloned and sequenced. The ssyB63 (Cs) mutation is an insertion mutation in nusB, while the nusB5 (Cs) mutation suppresses secY24, indicating that inactivation of nusB causes cold-sensitive cell growth as well as phenotypic suppression of secY24. The correct map position of nusB is 9.5 min rather than I I min as previously assigned. It is located at the distal end of an operon that contains a gene showing significant homology with a Bacillus subtilis gene involved in riboflavin biosynthesis.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1617-4623
    Keywords: Escherichia coli ; fdrA ; ftsH ; Multicopy suppressors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An Escherichia coli membrane protein, FtsH, has been implicated in several cellular processes, including integration of membrane proteins, translocation of secreted proteins, and degradation of some unstable proteins. However, how it takes part in such diverse cellular events is largely unknown. We previously isolated dominant negative ftsH mutations and proposed that FtsH functions in association with some other cellular factor(s). To test this proposal we isolated multicopy suppressors of dominant negative ftsH mutations. One of the multicopy suppressor clones contained an N-terminally truncated version of a new gene that was designated fdrA. The FdrA fragment suppressed both of the phenotypes — increased abnormal translocation of a normally cytoplasmic domain of a model membrane protein and retardation of protein export — caused by dominant negative FtsH proteins. The intact fdrA gene (11.9 min on the chromosome) directed the synthesis of a 60 kDa protein in vitro.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutants of Escherichia coli K12 that are partially or totally defective in induction of major heat-shock proteins and cannot grow at high temperature (42° C) were isolated by localized mutagenesis. These mutants carry a single mutation in the gene htpR (formerly hin) located at min 76 on the E. coli genetic map. Some mutants exhibit delayed (partial) induction of heat-shock proteins or require a higher temperature for induction than the wild type, whereas others are not induced under any of these conditions. The maximum temperature that allows growth varies among different mutants and is correlated with the residual induction capacity. Temperature-resistant revertants obtained from each mutant are fully or partially recovered in heat-shock induction. These results indicate that the inability of htpR mutants to grow at high temperature is due to the defect in heat-shock induction. In addition, a couple of mutants was found that produce significantly higher amounts of heat-shock proteins even at 30° C. The htpR gene has been cloned into plasmid pBR322 using the above mutants, and was localized to a DNA segment of 1.6 kilobase pairs. The mutants harboring certain palsmids that carry a part of htpR produce temperature-resistant recombinants at high frequency. This permits further localization of mutations within the htpR gene. Analysis of proteins encoded by each of the recombinant plasmids including the one carrying a previously isolated amber mutation (htpR165) led to the identification of a protein with an apparent molecular weight of about 36,000 daltons as the htpR gene product.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Regulation of the expression of the tryptophan (trp) operon of Escherichia coli integrated into the genome of transducing phage ϕ80pts was studied by infecting sensitive or immune bacteria and measuring the activities of tryptophan biosynthetic enzymes. In sensitive cells, expression of the trp operon in the genome of a transducing phage ϕ80pt190h is barely repressed by tryptophan and is mostly manifested by the “read through” transcription initiated at the phage promoter site, despite the fact that the phage carries the whole trp operon including the specific operator-promoter region. In ϕ80 lysogenic cells, however, transcription of the “early” genes is repressed by the phage immunity, and the trp operon is completely subject to the control by tryptophan. These results suggest that the repressor of the trp operon cannot prevent its transcription which was initiated at the preceding viral promoter on the same DNA. On the other hand, no appreciable read through transcription occurred with another transducing phage ϕ80pt66 (also carrying the trp operator-promoter region) upon infection of sensitive cells, and the trp operon was under normal control by tryptophan. In relation to these observations, a “turn off” control of early messenger RNA synthesis similar to that found with phage λ was observed in the transcription of the ϕ80 genome.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gene secY (or prlA) is essential for protein export across the cytoplasmic membrane of Escherichia coli. The protein product of secY has been identified using the gene cloned under the control of the pL promoter of phage λ in combination with the maxicell system. The protein was found to have some unusual properties. First, it is important not to heat the protein at 100°C in the SDS sample buffer for its subsequent detection by gel electrophoresis. Second, migration of the protein in SDS-polyacrylamide gel electrophoresis is variable depending on the gel compositions. Gels with stronger sieving effect give higher apparent molecular weights. These properties are similar to those of hydrophobic proteins of the cytoplasmic membrane, such as the lactose permease. Finally, a major fraction of the protein synthesized from the overproducing plasmid is degraded rapidly in vivo. The altered protein from the secY24 mutant gene is even more unstable. These results provide information which is basic for the dissection of the protein export machinery of the bacterial cell.
    Type of Medium: Electronic Resource
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