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  • 1
    Electronic Resource
    Electronic Resource
    Life in protein-rich environments: the relA-independent response of Streptococcus pyogenes to amino acid starvation (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 38 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Considering that group A streptococci are multiple auxotrophs that may encounter shortage of amino acids during specific stages of the infectious process, we studied their adaptive response to amino acid deprivation. We found that, in addition to the (p)ppGpp-mediated stringent response characterized previously, Streptococcus pyogenes exhibits a relA-independent response comprising transcriptional modulation of a specific subset of genes involved in pathogenesis. Genes/operons transcriptionally upregulated during starvation of both wild type and relA mutants included the two-component signal transduction system covRS, the positive regulator (ropB) of the pyrogenic exotoxin B gene, speB, the oligopeptide (opp) and dipeptide (dpp) permease systems and the pepB gene putatively involved in the intracellular processing of oligopeptides. Upregulation of covRS was accompanied by downregulation of ska, one of the target genes of the negative CovR regulator, and the net effect of amino acid starvation also favoured repression of speB. A significant feature of upregulated opp expression was stimulated readthrough transcription of the operon-internal oppA terminator, leading to increased mRNA levels for synthesis of the translocator complex relative to the substrate-binding protein. Based on these and previous results, a stimulus–response network is proposed that counteracts the stringent response and may enable the pathogen to mount a dynamic response to the protein-rich environment provided by its human host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02203.x
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  • 2
    Electronic Resource
    Electronic Resource
    Secretory proteins and Balbiani ring gene activities in salivary glands of Chironomus thummi larvae (1983)
    Springer
    Chromosoma 88 (1983), S. 16-23 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The salivary gland cells of Chironomus larvae synthesize almost exclusively secretory proteins, for constructing the tubes in which they live. The secretory proteins of C. thummi contain a high percentage of basic amino acids, chiefly lysine (about 20%), and consist of two main giant secretory proteins of about 1,000 kd, called sp-Ia and sp-Ib, and a number of low-molecular-weight fractions, sp-180, sp-150, sp-36, sp-18, and sp-15. Galactose treatment shows that the synthesis of sp-I fractions is correlated with the puffing of Balbiani rings, BRb and BRc, and with the relative abundance of Balbiani ring RNA transcripts in the cytoplasm. The sp-I fractions, which appear to represent real polypeptides, display individual- and strain-specific size variations. Cleavage of sp-I proteins with cyanogen bromide (CNBr) yields peptides of about 17 kd and peptide ladders composed of 8–10 multimers of this 17kd “basic sequence”. These properties are typical for proteins encoded by the giant, internally repeated Balbiani ring genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329499
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  • 3
    Electronic Resource
    Electronic Resource
    The lppC gene of Streptococcus equisimilis encodes a lipoprotein that is homologous to the e (P4) outer membrane protein from Haemophilus influenzae (1997)
    Springer
    Medical microbiology and immunology 186 (1997), S. 63-73 
    Details
    ISSN: 1432-1831
    Keywords: Key wordsStreptococcus equisimilis H46A ; lppC gene ; Nucleotide sequence ; Membrane lipoprotein ; Heterologous expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the cloning, sequencing, and analysis of a novel chromosomal gene of Streptococcus equisimilis strain H46A that codes for a membrane lipoprotein, designated LppC. The lppC gene is located 3′ adjacent to, and co-oriented with, the unrelated gapC gene that encodes the previously characterized glyceraldehyde-3-phosphate dehydrogenase. Sequencing of lppC revealed an 855-bp open reading frame that predicted a 32.4-kDa polypeptide possessing a potential lipoprotein signal sequence and modification site (VTGC). Signal sequence processing of LppC synthesized in the homologous host or expressed from plasmid pLPP2 in Escherichia coli was sensitive to globomycin, a selective inhibitor of lipoprotein-specific signal peptidase II. Subcellular localization of LppC using polyclonal antibodies raised to the hexahistidyl-tagged protein proved LppC to be tightly associated with the cytoplasmic membrane of S. equisimilis and with the outer membrane of E. coli JM109 (pLPP2). Southern, Northern and Western analyses indicated that lpp was conserved in S. pyogenes, and transcribed independently of gap as monocistronic 0.9-kb mRNA from a σ 70-like consensus promoter. Database searches found homology of LppC to the hel gene-encoded outer membrane protein e (P4) from Haemophilus influenzae to which it exhibits 58% sequence similarity. However, unlike the hel gene, lppC was unable to complement hemA mutants of E. coli for growth on hemin as sole porphyrin source in aerobic conditions. Furthermore, neither the wild type nor an lppC insertion mutant of S. equisimilis could grow on hemin in iron-limited medium. These results, together with findings indicating that S. equisimilis H46A had no absolute requirement for iron, led us to conclude that lppC, in contrast to hel, is not involved in hemin utilization and has yet to be assigned a function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004300050047
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  • 4
    Electronic Resource
    Electronic Resource
    Conservation of the organization of the streptokinase gene region among pathogenic streptococci (1995)
    Springer
    Medical microbiology and immunology 184 (1995), S. 139-146 
    Details
    ISSN: 1432-1831
    Keywords: Streptococcus equisimilis ; S. pyogenes ; S. uberis ; Streptokinase gene region ; Southern hybridization ; Genome organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using ten gene-specific probes from the cloned and sequenced streptokinase gene (skc) region (8 931 bp) of Streptococcus equisimilis H46A, a human serogroup C strain, the conservation of these genes and their linkage relationships were studied by Southern hybridization in pathogenic streptococci differing taxonomically, serologically, in regard to their host range, and in the class of plasminogen activator produced. The results indicate that in S. pyogenes (strains A374, NZ131 and SF130/13) and a human group G strain (G19 908) both gene content and gene order as determined for H46A (dexB-abc-lrp-skc-orf1-rel) are preserved. The same is true of an equine S, equisimilis isolate (87-542-W), the streptokinase gene of which has been shown to hybridize detectably with skc, a result at variance with that obtained previously by others. In contrast, the chromosomal DNA of three S. uberis strains (0140J, C198, C216) of bovine origin, two of which produced a plasminogen activator different from streptokinase, hybridized only with dexB-, abc- and rel-specific probes, and the homologues of these genes appeared to lie close to each other. The maintenance of the organization of the streptokinase gene region in strains differing in overall chromosomal character suggests that this gene arrangement is of selective advantage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224351
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  • 5
    Electronic Resource
    Electronic Resource
    Transcription termination of the streptokinase gene of Streptococcus equisimilis H46A: bidirectionality and efficiency in homologous and heterologous hosts (1995)
    Springer
    Molecular genetics and genomics 246 (1995), S. 374-380 
    Details
    ISSN: 1617-4623
    Keywords: Streptococcus equisimilis H46A ; Escherichia coli ; skc gene ; rel-orf1 genes ; Bidirectional transcription terminator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Streptococcus equisimilis H46A, a hypersymmetrical transcription terminator with bidirectional activity was localized between the translational termination codons of the streptokinase gene, skc, and the rel-orf1 genes. These two transcription units are oriented towards each other, and under normal conditions the skc mRNA level exceeds that of the rel-orf1 genes by a factor of at least 1000. Reporter vectors based on the promoterless cat gene were constructed by transcriptional fusion of skc to cat, such that the region between the two genes contained the terminator in skc orientation or in rel-orf1 orientation. Additionally, skc and cat were fused directly, with deletion of the terminator. The reporter vectors were designed to be capable of being studied either as multicopy plasmids in Escherichia coli or in single copy following integration, via skc, into the S. equisimilis chromosome. Chloramphenicol acetyl transferase (CAT) activity assays in conjunction with determination of chloramphenicol resistance levels and Northern hybridization analysis showed that the terminator is active in either host and orientation. However, termination efficiency was host dependent, with high terminator strength being observed in the homologous streptococcal background and appreciable readthrough occurring in E. coli. The extent of transcriptional readthrough was dependent upon terminator orientation, with termination being more efficient in rel-orf1 polarity. The results suggest that, in S. equisimilis, transcription of both skc and rel-orf1 is efficiently terminated by a common signal, and that these genes are largely protected from convergent transcription, which otherwise would seem to be particularly detrimental to the weakly expressed rel-orf1 genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288611
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  • 6
    Electronic Resource
    Electronic Resource
    Genetic organization of the streptokinase region of the Streptococcus equisimilis H46A chromosome (1993)
    Springer
    Molecular genetics and genomics 241 (1993), S. 129-140 
    Details
    ISSN: 1617-4623
    Keywords: Streptococcus equisimilis H46A ; Streptokinase region ; Nucleotide sequence ; rel gene ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The complete nucleotide sequences of four genes and one open reading frame (ORF1) adjacent to the streptokinase gene, skc, from Streptococcus equisimilis H46A were determined. These genes are encoded on the opposite DNA strand to skc and are arranged as follows: dexB-abc-lrp-skc-ORF1-rel. The dexB gene, coding for an α-glucosidase (Mr 61733), and abc, encoding an ABC transporter (Mr 42080), are similar to the dexB and msmK genes, respectively, from the multiple sugar metabolism operon of S. mutans. The lrp gene specifies a leucine-rich protein (Mr 32302) that has a leucine-zipper motif at its C-terminus. The function of the Lrp protein is not known but appeared to be detrimental when overexpressed in Escherichia coli. Although lrp appears not to be an essential gene, as judged by plasmid insertion mutagenesis, it is conserved in all streptococcal strains carrying a streptokinase gene. The rel gene showed significant homology to the E. coli relA and spoT genes involved in the stringent response to amino acid deprivation. Multiple alignment of the amino acid sequences of Rel (Mr 83913), RelA and SpoT revealed 59.4% homology of the primary structures. Northern hybridiziatioo analyses of the genes in the skc region showed skc to be transcribed most abundantly. In addition to transcripts for skc, monocistronic mRNAs were detected for all three genes divergently transcribed from skc. Although there was also some read-through transcription from lrp into abc, and from abc into dexB, the transcription pattern suggests a high degree of transcriptional and functional independence not only of skc but also abc and dexB. Prominent structural features in intergenic regions included a static DNA bending locus located upstream and a putative bidirectional transcription terminator downstream of skc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280210
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