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  • 1
    Electronic Resource
    Electronic Resource
    Crystallization of the regulatory and effector domains of the key sporulation response regulator Spo0A (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 671-676 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The key response-regulator gene of sporulation, spo0A, has been cloned from Bacillus stearothermophilus and the encoded protein purified. The DNA-binding and phospho-acceptor domains of Spo0A have been prepared by tryptic digestion of the intact protein and subsequently crystallized in forms suitable for X-ray crystallographic studies. The DNA-binding domain has been crystallized in two forms, one of which diffracts X-rays to beyond 2.5 Å spacing. The crystals of the phospho-acceptor domain diffract X-rays beyond 2.0 Å spacing using synchrotron radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444998012682
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon-source regulation of virulence gene expression in Listeria monocytogenes (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: All known virulence genes of Listeria monocytogenes are under positive regulation by the transcription factor PrfA. Previous work employing the L. monocytogenes strain NCTC7973 suggested that the disaccharide cellobiose might serve as a specific ‘signature molecule’ which functions to prevent activation of the PrfA-controlled regulon in a soil environment. We have examined three other L. monocytogenes strains, 10403S, LO28 and EGD, all commonly regarded as wild-type isolates, and find that NCTC7973 is anomalous with respect to the effect of carbohydrates on the expression of PrfA-controlled gene expression. In the case of 10403S, LO28 and EGD, several other readily metabolized mono- and disaccharides are as effective as cellobiose in repressing expression of the PrfA-controlled gene hly, indicating that the cellobiose effect is not specific, and suggesting that NCTC7973 may be a partially deregulated variant. Moreover, concentrations of cellobiose and other sugars required for repression of hly expression (〉 1 mM) were found to significantly enhance growth of L. monocytogenes cultures, suggesting that the repression phenomenon probably results from a metabolic effect of sugar utilization rather than a signal-sensing response. Thus the previously reported cellobiose effect may reflect an aspect of a more global mechanism of catabolite repression in L. monocytogenes. Although cellobiose represses expression of hly and plcA at the level of transcript accumulation, quantitative Western blot analysis indicates that cellobiose has no effect on PrfA levels. These results are consistent with a model in which PrfA activity is controlled by interaction with a hypothetical cofactor, the synthesis or depletion of which is responsive to the presence of readily metabolized carbohydrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2711634.x
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  • 3
    Electronic Resource
    Electronic Resource
    Spo0A directly controls the switch from acid to solvent production in solvent-forming clostridia (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The spo0A genes of Clostridium beijerinckii NCIMB 8052 and Clostridium cellulolyticum ATCC 35319 were isolated and characterized. The C-terminal DNA-binding domains of the predicted products of spo0A from these two organisms, as well as 16 other taxonomically diverse species of Bacillus and Clostridium, show extensive amino acid sequence conservation (56% identity, 65% similarity over 104 residues). A 12-amino-acid motif (SRVERAIRHAIE) that forms the putative DNA recognition helix is particularly highly conserved, suggesting a common DNA target. Insertional inactivation of spo0A in C. beijerinckii blocked the formation of solvents (as well as spores and granulose). Sequences resembling Spo0A-binding motifs (TGNCGAA) are found in the promoter regions of several of the genes whose expression is modulated at the onset of solventogenesis in Clostridium acetobutylicum and C. beijerinckii. These include the upregulated adc gene, encoding acetoacetate decarboxylase (EC 4.1.1.4), and the downregulated ptb gene, encoding phosphotransbutyrylase (EC 2.3.1.c). In vitro gel retardation experiments using C. acetobutylicum adc and C. beijerinckii ptb promoter fragments and recombinant Bacillus subtilis and C. beijerinckii Spo0A suggested that adc and ptb are directly controlled by Spo0A. The binding affinity was reduced when the 0A boxes were destroyed, and enhanced when they were modified to conform precisely to the consensus sequence. In vivo analysis of wild-type and mutagenized promoters transcriptionally fused to the gusA reporter gene in C. beijerinckii validated this hypothesis. Post-exponential phase expression from the mutagenized adc promoter was substantially reduced, whereas expression from the mutagenized ptb promoter was not shut down at the end of exponential growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02071.x
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and function of the Bacillus SpoIIE protein and its localization to sites of sporulation septum assembly (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Functioning of the spoIIE locus of Bacillus subtilis is required for formation of a normal polar septum during sporulation and for activation of the transcription factor σF, which directs early forespore-specific gene expression. We have determined the DNA sequence of the wild type and several mutant alleles of the spoIIE gene of B. subtilis and sequenced a substantial portion of its presumptive homologue in Bacillus megaterium. We show that the spoIIE locus encodes a single large protein with a predicted molecular mass of 92 kDa. Each of five point-mutation alleles, which have traditionally defined the locus, and two transposon-generated mutations were shown to fall within the coding sequence for the 92 kDa gene product or within sequences expected to be required for its expression. The amino-terminal portion of the predicted SpoIIE gene product, comprising approximately 40% of the protein, is extremely hydrophobic and is expected to contain up to 12 membrane-spanning segments. The remainder of the protein contains no hydrophobic segments long enough to span a lipid bilayer and is therefore presumed to comprise one or more globular, aqueous-phase exposed domains. An in-frame fusion joining the 3′ end of the B. megaterium spoIIE coding sequence to the 5′ end of gfp, a gene encoding the green fluorescent protein (GFP) of Aquorea victoria, resulted in a strong, sporulation-specific fluorescent signal localized to the sites of sporulation septum assembly. We speculate that SpoIIE plays a role in assembling the sporulation septum, perhaps determining the special properties of the structure that permit intercompartment signalling during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.433963.x
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of spo0A homologues in diverse Bacillus and Clostridium species identifies a probable DNA-binding domain (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 14 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Spo0A is a phosphorylation-activated transcription factor of Bacillus subtilis. It is a member of the response regulator super-family of bacterial signal transduction proteins and controls many of the changes in gene expression that occur during the transition into stationary phase and during the initiation of speculation. To identify the domains of Spo0A most critical for determining its structural and functional features, presumptive homologues of the spo0A gene were characterized in a collection of eight Bacillus species and six Clostridium species representing phylogenetically diverse members of these genera. An alignment of the partial or complete DNA sequences of these homologues revealed three regions of especially high conservation in the effector domain. We speculate that the most highly conserved of these corresponds to the recognition helix of a putative helix-turn-helix motif, and, therefore, represents the actual DNA-contacting surface of the protein. In the case of homologues identified in Bacillus anthracis and Clostridium acetobutylicum and retrieved by polymerase chain reaction amplification, we confirmed by gene-disruption analysis that the homologue actually is required for initiation of sporulation. Apparent homologues of the B. subtilis spolVB gene were also discovered immediately upstream from the spo0A homologues in all Bacillus and Clostridium species examined. The discovery of homologues of B. subtilis sporulation genes in these diverse species implies that the gene products required for specifying pathways of sporulation-specific gene activation and for determining key morphogenetic changes may be highly conserved and suggests that an approach similar to that undertaken here might be used as a general strategy to retrieve and compare their gene sequences. Exhaustive efforts to detect a spo0A-like gene in non-endospore formers, including close relatives of Bacillus such as Listeria and Staphylococcus, were uniformly unsuccessful, suggesting that regulation of gene activity during the transition into stationary phase mediated by Spo0A-like proteins may be exclusive to the endospore-forming bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb02176.x
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  • 6
    Electronic Resource
    Electronic Resource
    High-level expression and purification of mature HIV-1 protease in Escherichia coli under control of the araBAD promoter (1992)
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 205-210 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A 1.3-kb segment of Escherichia coli DNA containing the regulatory gene, araC, and the promoter of the araBAD operon was amplified by the polymerase chain reaction (PCR) and cloned into pUC18, resulting in plasmid pKB130 that produced the α fragment of β-galactosidase upon addition of L-arabinose (L-ara). A synthetic gene for human immunodeficiency virus (HIV)-1 preprotease was placed downstream of the araBAD promoter in pKB130 to create a translational fusion inducible by addition of L-ara. The fusion protein correctly autoprocessed in vivo to yield a mature 99-amino-acid HIV-1 protease, which was found predominantly in inclusion bodies. This material could be refolded to an active form, which was purified to homogeneity. A small fraction of the protease was expressed in vivo as a soluble active form, which allowed the monitoring of expression during fermentation by a rapid and simple whole cell assay employing an HIV-1 protease-specific fluorogenic substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178172
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  • 7
    Electronic Resource
    Electronic Resource
    On limit cycles inn-order direct-form digital filters (1991)
    Springer
    Circuits, systems and signal processing 10 (1991), S. 153-161 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The relationship between the elements in the vector of any limit cycle due to rounding in ann-order direct-form digital filter is established. Some bounds on the elements in such vectors are also determined. Sufficient conditions for the accessibility of period-r limit cycles due to rounding inn-order digital filters are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01183768
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  • 8
    Electronic Resource
    Electronic Resource
    On limit cycles of second-order sigma-delta modulators with constant input (1995)
    Springer
    Circuits, systems and signal processing 14 (1995), S. 675-688 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Exact analysis of second-order sigma-delta modulators with constant input is presented. Some properties of general limit cycles are established. Sufficient conditions for the existence of a general class of limit cycles of the state vectors of the modulator are determined. The conditions interrelate the input, an initial vector, and the period of the limit cycle. Also, sufficient conditions are determined for a class of initial condition vectors to converge to a limit cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01213964
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  • 9
    Electronic Resource
    Electronic Resource
    N-order direct form digital filters with integer arithmetic (1993)
    Springer
    Circuits, systems and signal processing 12 (1993), S. 441-452 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract For direct form digital filters with integer arithmetic, a characterization of the initial condition vector and state vectorX(ρ), for a fixedρ,ρ 〉 1, is established without the intermediate state vectors. This is used to determine initial conditions for stability and initial conditions for convergence to a limit cycle. Also, several properties of limit cycles are proven.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01223320
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of the genes and attachment sites for site-specific integration of plasmid pSE101 in Saccharopolyspora erythraea and Streptomyces lividans (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 185-193 
    Details
    ISSN: 1617-4623
    Keywords: Streptomyces lividans ; Site-specific recombination ; Integrase ; pSE101 ; Saccharopolyspora erythraea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 11.3 kb plasmid pSE101 integrates into the chromosome of Saccharopolyspora erythraea at a specific attB site and into the chromosome of Streptomyces lividans at many sites. Multisite integration in S. lividans was also observed when a 1.9 kb segment of pSE101 containing attP and adjacent plasmid sequence was used to transform a pSE101− S. lividans host. Nucleotide sequencing of this segment revealed the presence of a complete open reading frame (ORF) designated int, encoding a putative polypeptide of 448 amino acids that shows similarities to site-specific recombinases of the integrase family. Sequencing of the 1.3 kb segment upstream of int revealed the presence of three additional ORFs: the one most distal to int encodes a putative 76 amino acid basic polypeptide analogous to the Xis proteins of a number of bacteriophages. Nucleotide sequencing of attP, and the attB, attL and attR sites from Sac. erythraea revealed a 46 by sequence common to all sites with no duplications of chromosomal sequences in the integrated state. A putative structural gene for a tRNAThr was found to overlap the 46 by common sequence at attB. Sequencing of four pSE101 integration sites (attB′) and corresponding attL′ and attR′ sites in S. lividans showed that the 46 by sequence was present at each attR′ site, whereas only the first three bases, CTT, were retained at each attL′ and attB′ site. A feature common to the four attB′ sites and to attB is a highly conserved 21 by segment with inverted repeats flanking the CTT sequence. This indicates that crossover at each attB′ site in S. lividans employed attP and a site within a 5 by sequence in attB′ and suggests that the secondary structure of the 21 by sequence is important for site-specific integration at attB or attB′.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391012
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