scholarly journals Global versus Local Regulatory Roles for Lrp-Related Proteins: Haemophilus influenzae as a Case Study

2001 ◽  
Vol 183 (13) ◽  
pp. 4004-4011 ◽  
Author(s):  
Devorah Friedberg ◽  
Michael Midkiff ◽  
Joseph M. Calvo
Keyword(s):  
Amino Acid ◽  
Haemophilus Influenzae ◽  
Regulatory Protein ◽  
Enteric Bacteria ◽  
Regulatory Role ◽  
Regulatory Function ◽  
Ecological Niches ◽  
E Coli ◽  
Sequence Identity ◽  
Related Proteins

ABSTRACT Lrp (leucine-responsive regulatory protein) plays a global regulatory role in Escherichia coli, affecting expression of dozens of operons. Numerous lrp-related genes have been identified in different bacteria and archaea, includingasnC, an E. coli gene that was the first reported member of this family. Pairwise comparisons of amino acid sequences of the corresponding proteins shows an average sequence identity of only 29% for the vast majority of comparisons. By contrast, Lrp-related proteins from enteric bacteria show more than 97% amino acid identity. Is the global regulatory role associated withE. coli Lrp limited to enteric bacteria? To probe this question we investigated LrfB, an Lrp-related protein fromHaemophilus influenzae that shares 75% sequence identity with E. coli Lrp (highest sequence identity among 42 sequences compared). A strain of H. influenzae having anlrfB null allele grew at the wild-type growth rate but with a filamentous morphology. A comparison of two-dimensional (2D) electrophoretic patterns of proteins from parent and mutant strains showed only two differences (comparable studies withlrp + and lrp E. coli strains by others showed 20 differences). The abundance of LrfB in H. influenzae, estimated by Western blotting experiments, was about 130 dimers per cell (compared to 3,000 dimers per E. colicell). LrfB expressed in E. coli replaced Lrp as a repressor of the lrp gene but acted only to a limited extent as an activator of the ilvIH operon. Thus, although LrfB resembles Lrp sufficiently to perform some of its functions, its low abundance is consonant with a more local role in regulating but a few genes, a view consistent with the results of the 2D electrophoretic analysis. We speculate that an Lrp having a global regulatory role evolved to help enteric bacteria adapt to their ecological niches and that it is unlikely that Lrp-related proteins in other organisms have a broad regulatory function.

scholarly journals Purification and Characterization of Sa-Lrp, a DNA-Binding Protein from the Extreme Thermoacidophilic ArchaeonSulfolobus acidocaldarius Homologous to the Bacterial Global Transcriptional Regulator Lrp

2000 ◽  
Vol 182 (13) ◽  
pp. 3661-3672 ◽  
Author(s):  
Julius Enoru-Eta ◽  
Daniel Gigot ◽  
Thia-Lin Thia-Toong ◽  
Nicolas Glansdorff ◽  
Daniel Charlier
Keyword(s):  
Amino Acid ◽  
Dna Binding ◽  
Binding Capacity ◽  
Large Fraction ◽  
Regulatory Protein ◽  
Physiological Role ◽  
Transcriptional Regulator ◽  
Stationary Growth Phase ◽  
Heat Inactivation ◽  
E Coli

ABSTRACT Archaea, constituting the third primary domain of life, harbor a basal transcription apparatus of the eukaryotic type, whereas curiously, a large fraction of the potential transcription regulation factors appear to be of the bacterial type. To date, little information is available on these predicted regulators and on the intriguing interplay that necessarily has to occur with the transcription machinery. Here, we focus on Sa-lrp of the extremely thermoacidophilic crenarchaeote Sulfolobus acidocaldarius, encoding an archaeal homologue of the Escherichia colileucine-responsive regulatory protein Lrp, a global transcriptional regulator and genome organizer. Sa-lrp was shown to produce a monocistronic mRNA that was more abundant in the stationary-growth phase and produced in smaller amounts in complex medium, this down regulation being leucine independent. We report on Sa-Lrp protein purification from S. acidocaldarius and from recombinantE. coli, both identified by N-terminal amino acid sequence determination. Recombinant Sa-Lrp was shown to be homotetrameric and to bind to its own control region; this binding proved to be leucine independent and was stimulated at high temperatures. Interference binding experiments suggested an important role for minor groove recognition in the Sa-Lrp–DNA complex formation, and mutant analysis indicated the importance for DNA binding of the potential helix-turn-helix motif present at the N terminus of Sa-Lrp. The DNA-binding capacity of purified Sa-Lrp was found to be more resistant to irreversible heat inactivation in the presence ofl-leucine, suggesting a potential physiological role of the amino acid as a cofactor.

scholarly journals Expression of the Streptomyces coelicolor SoxR Regulon Is Intimately Linked with Actinorhodin Production

2010 ◽  
Vol 192 (24) ◽  
pp. 6428-6438 ◽  
Author(s):  
Rica Dela Cruz ◽  
Yang Gao ◽  
Sahitya Penumetcha ◽  
Rebecca Sheplock ◽  
Katherine Weng ◽  
...  
Keyword(s):  
Streptomyces Coelicolor ◽  
Enteric Bacteria ◽  
Ecological Niches ◽  
Active Metabolites ◽  
E Coli ◽  
Redox Active ◽  
Tailoring Enzymes ◽  
And Function ◽  
Active Precursor

ABSTRACT The [2Fe-2S]-containing transcription factor SoxR is conserved in diverse bacteria. SoxR is traditionally known as the regulator of a global oxidative stress response in Escherichia coli, but recent studies suggest that this function may be restricted to enteric bacteria. In the vast majority of nonenterics, SoxR is predicted to mediate a response to endogenously produced redox-active metabolites. We have examined the regulation and function of the SoxR regulon in the model antibiotic-producing filamentous bacterium Streptomyces coelicolor. Unlike the E. coli soxR deletion mutant, the S. coelicolor equivalent is not hypersensitive to oxidants, indicating that SoxR does not potentiate antioxidant defense in the latter. SoxR regulates five genes in S. coelicolor, including those encoding a putative ABC transporter, two oxidoreductases, a monooxygenase, and a possible NAD-dependent epimerase/dehydratase. Expression of these genes depends on the production of the benzochromanequinone antibiotic actinorhodin and requires intact [2Fe-2S] clusters in SoxR. These data indicate that actinorhodin, or a redox-active precursor, modulates SoxR activity in S. coelicolor to stimulate the production of a membrane transporter and proteins with homology to actinorhodin-tailoring enzymes. While the role of SoxR in S. coelicolor remains under investigation, these studies support the notion that SoxR has been adapted to perform distinct physiological functions to serve the needs of organisms that occupy different ecological niches and face different environmental challenges.

scholarly journals Class A Carbapenemase FPH-1 from Francisella philomiragia

2012 ◽  
Vol 56 (6) ◽  
pp. 2852-2857 ◽  
Author(s):  
Marta Toth ◽  
Viktoria Vakulenko ◽  
Nuno T. Antunes ◽  
Hilary Frase ◽  
Sergei B. Vakulenko
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Amino Acid Sequence Identity ◽  
Content Type ◽  
E Coli ◽  
New Class ◽  
Sequence Identity ◽  
Class A ◽  
High Level ◽  
Level Resistance

ABSTRACTFPH-1 is a new class A carbapenemase fromFrancisella philomiragia. It produces high-level resistance to penicillins and the narrow-spectrum cephalosporin cephalothin and hydrolyzes these β-lactam antibiotics with catalytic efficiencies of 106to 107M−1s−1. When expressed inEscherichia coli, the enzyme confers resistance to clavulanic acid, tazobactam, and sulbactam and hasKivalues of 7.5, 4, and 220 μM, respectively, against these inhibitors. FPH-1 increases the MIC of the monobactam aztreonam 256-fold and the MIC of the broad-spectrum cephalosporin ceftazidime 128-fold, while the MIC of cefoxitin remains unchanged. MICs of the carbapenem antibiotics imipenem, meropenem, doripenem, and ertapenem are elevated 8-, 8-, 16-, and 64-fold, respectively, against anE. coliJM83 strain producing the FPH-1 carbapenemase. The catalytic efficiencies of the enzyme against carbapenems are in the range of 104to 105M−1s−1. FPH-1 is 77% identical to the FTU-1 β-lactamase fromFrancisella tularensisand has low amino acid sequence identity with other class A β-lactamases. Together with FTU-1, FPH-1 constitutes a new branch of the prolific and ever-expanding class A β-lactamase tree.

scholarly journals Substrate Specificity of the Escherichia coli Outer Membrane Protease OmpP

2006 ◽  
Vol 189 (2) ◽  
pp. 522-530 ◽  
Author(s):  
Bum-Yeol Hwang ◽  
Navin Varadarajan ◽  
Haixin Li ◽  
Sarah Rodriguez ◽  
Brent L. Iverson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Outer Membrane ◽  
Amino Acid Sequence Identity ◽  
Catalytic Efficiency ◽  
Wild Type ◽  
Peptide Substrate ◽  
Peptide Substrates ◽  
E Coli ◽  
Sequence Identity

ABSTRACT Escherichia coli OmpP is an F episome-encoded outer membrane protease that exhibits 71% amino acid sequence identity with OmpT. These two enzymes cleave substrate polypeptides primarily between pairs of basic amino acids. We found that, like OmpT, purified OmpP is active only in the presence of lipopolysaccharide. With optimal peptide substrates, OmpP exhibits high catalytic efficiency (k cat/Km = 3.0 × 106 M−1s−1). Analysis of the extended amino acid specificity of OmpP by substrate phage revealed that both Arg and Lys are strongly preferred at the P1 and P1′ sites of the enzyme. In addition, Thr, Arg, or Ala is preferred at P2; Leu, Ala, or Glu is preferred at P4; and Arg is preferred at P3′. Notable differences in OmpP and OmpT specificities include the greater ability of OmpP to accept Lys at the P1 or P1′, site as well as the prominence of Ser at P3 in OmpP substrates. Likewise, the OmpP P1 site could better accommodate Ser; as a result, OmpP was able to cleave a peptide substrate between Ser-Arg about 120 times more efficiently than was OmpT. Interestingly, OmpP and OmpT cleave peptides with three consecutive Arg residues at different sites, a difference in specificity that might be important in the inactivation of cationic antimicrobial peptides. Accordingly, we show that the presence of an F′ episome results in increased resistance to the antimicrobial peptide protamine both in ompT mutants and in wild-type E. coli cells.

scholarly journals gyrA Mutations Associated with Fluoroquinolone Resistance in Eight Species ofEnterobacteriaceae

1998 ◽  
Vol 42 (10) ◽  
pp. 2661-2667 ◽  
Author(s):  
Linda M. Weigel ◽  
Christine D. Steward ◽  
Fred C. Tenover
Keyword(s):  
Amino Acid ◽  
Klebsiella Oxytoca ◽  
Enteric Bacteria ◽  
Amino Acid Sequences ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Single Point Mutation ◽  
Amino Acid Substitutions ◽  
E Coli ◽  
Type Strains

ABSTRACT Fluoroquinolone resistance (FQ-R) in clinical isolates ofEnterobacteriaceae species has been reported with increasing frequency in recent years. Two mechanisms of FQ-R have been identified in gram-negative organisms: mutations in DNA gyrase and reduced intracellular drug accumulation. A single point mutation ingyrA has been shown to reduce susceptibility to fluoroquinolones. To determine the extent of gyrA mutations associated with FQ-R in enteric bacteria, one set of oligonucleotide primers was selected from conserved sequences in the flanking regions of the quinolone resistance-determining regions (QRDR) ofEscherichia coli and Klebsiella pneumoniae. This set of primers was used to amplify and sequence the QRDRs from 8Enterobacteriaceae type strains and 60 fluoroquinolone-resistant clinical isolates of Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, E. coli, K. pneumoniae,Klebsiella oxytoca, Providencia stuartii, andSerratia marcescens. Although similarity of the nucleotide sequences of seven species ranged from 80.8 to 93.3%, when compared with that of E. coli, the amino acid sequences of the gyrA QRDR were highly conserved. Conservative amino acid substitutions were detected in the QRDRs of the susceptible type strains of C. freundii, E. aerogenes, K. oxytoca (Ser-83 to Thr), and P. stuartii (Asp-87 to Glu). Strains with ciprofloxacin MICs of >2 μg/ml expressed amino acid substitutions primarily at the Gly-81, Ser-83, or Asp-87 position. Fluoroquinolone MICs varied significantly for strains exhibiting identical gyrA mutations, indicating that alterations outside gyrA contribute to resistance. The type and position of amino acid alterations also differed among these six genera. High-level FQ-R frequently was associated with singlegyrA mutations in all species ofEnterobacteriaceae in this study except E. coli.

scholarly journals Identification and Characterization of thefis Operon in Enteric Bacteria

1998 ◽  
Vol 180 (22) ◽  
pp. 5932-5946 ◽  
Author(s):  
Michael B. Beach ◽  
Robert Osuna
Keyword(s):  
Amino Acid ◽  
Genomic Sequence ◽  
Erwinia Carotovora ◽  
Enteric Bacteria ◽  
Integration Host Factor ◽  
Amino Acid Sequences ◽  
Reading Frame ◽  
E Coli

ABSTRACT The small DNA binding protein Fis is involved in several different biological processes in Escherichia coli. It has been shown to stimulate DNA inversion reactions mediated by the Hin family of recombinases, stimulate integration and excision of phage λ genome, regulate the transcription of several different genes including those of stable RNA operons, and regulate the initiation of DNA replication at oriC. fis has also been isolated from Salmonella typhimurium, and the genomic sequence of Haemophilus influenzae reveals its presence in this bacteria. This work extends the characterization of fis to other organisms. Very similar fis operon structures were identified in the enteric bacteria Klebsiella pneumoniae, Serratia marcescens, Erwinia carotovora, andProteus vulgaris but not in several nonenteric bacteria. We found that the deduced amino acid sequences for Fis are 100% identical in K. pneumoniae, S. marcescens,E. coli, and S. typhimurium and 96 to 98% identical when E. carotovora and P. vulgaris Fis are considered. The deduced amino acid sequence forH. influenzae Fis is about 80% identical and 90% similar to Fis in enteric bacteria. However, in spite of these similarities, the E. carotovora, P. vulgaris, and H. influenzae Fis proteins are not functionally identical. An open reading frame (ORF1) precedingfis in E. coli is also found in all these bacteria, and their deduced amino acid sequences are also very similar. The sequence preceding ORF1 in the enteric bacteria showed a very strong similarity to the E. coli fis P region from −53 to +27 and the region around −116 containing an ihfbinding site. Both β-galactosidase assays and primer extension assays showed that these regions function as promoters in vivo and are subject to growth phase-dependent regulation. However, their promoter strengths vary, as do their responses to Fis autoregulation and integration host factor stimulation.

Existence and Decontamination of HVC, Infectious Enteric Bacteria and Parasites in Sewaged Soils

2014 ◽  
Vol 3 (1) ◽  
pp. 150-158 ◽  
Author(s):  
Mohey A. Hassanain ◽  
Nawal A. Hassanain ◽  
Esam A. Hobballa ◽  
Fatma H. Abd- El Zaher ◽  
Mohamed Saber M. Saber
Keyword(s):  
Soil Sample ◽  
Potassium Permanganate ◽  
Enteric Bacteria ◽  
Sewage Effluent ◽  
Calcium Hypochlorite ◽  
Sand Soil ◽  
E Coli ◽  
Surface Sample ◽  
Loamy Sand Soil ◽  
Sewage Farm

A surface sample representing a high contaminated loamy sand soil irrigated with sewage effluent since 30 years and was cultivated with artichoke was collected from Abu-Rawash sewage farm. The existence of HVC, enteric infectious bacteria and parasites in sewaged soil found to be negative for the forward and positive for the latter's. Out of the 30 samples separated from the sewaged soil sample, only 3 samples contained parasitic fauna of developed and undeveloped Ascaris (10%) and five samples contained Entamoeba coli. Results showed that the number of Ascaris eggs/gm soil was 0.017 and the number of E. coli/gm was 0.26. Decontamination of soil parasites was effective using either calcium hypochlorite or potassium permanganate. Salmonella, Vibrio and Campelobacter were detected in the high contaminated sewaged soil and survived for 120 days in the sewaged soil under all control and bioremediated treatments irrigated with either sewage effluent or water.

Use of gene probes for the detection of quiescent enteric bacteria in marine and fresh waters

1995 ◽  
Vol 31 (5-6) ◽  
pp. 291-298
Author(s):  
Sally A. Anderson ◽  
Gillian D. Lewis ◽  
Michael N. Pearson
Keyword(s):  
Membrane Filtration ◽  
Enteric Bacteria ◽  
Probe Method ◽  
Detection Methods ◽  
23S Rrna ◽  
Specific Gene ◽  
Gene Probe ◽  
Selective Media ◽  
Selective Enrichment ◽  
E Coli

Specific gene probe detection methods that utilise a non-selective culturing step were tested for the ability to recognise the presence of quiescent enteric bacteria (Escherichia coli and Enterococcus faecalis ) within illuminated freshwater and seawater microcosms. An E. coli specific uidA gene probe and a 23S rRNA oligonucleotide probe for Enterococci were compared with recoveries using membrane filtration and incubation on selective media (mTEC and mE respectively). From these microcosm experiments a greater initial detection (from 4 hours to 1 day) of E. coli and Ent. faecalis using gene probe methods was observed. Additionally, a comparison of E. coli direct viable counts (DVC) in sunlight exposed microcosms with recoveries by selective media and gene probe methods revealed a large number of viable non-culturable cells. This suggests that enumeration of E. coli by a gene probe method is limited by the replication of the bacteria during the initial non-selective enrichment step. The detection of stressed Ent. faecalis by the oligonucleotide gene probe method was significantly greater than recovery on selective mE agar, indicating an Enterococci non-growth phase.

The Regulatory Function of the Molecular Chaperone Hsp90 in the Cell Wall Integrity of Pathogenic Fungi

2018 ◽  
Vol 16 (1) ◽  
pp. 44-53
Author(s):  
Marina Campos Rocha ◽  
Camilla Alves Santos ◽  
Iran Malavazi
Keyword(s):  
Cell Wall ◽  
Antifungal Therapy ◽  
Molecular Chaperone ◽  
Regulatory Protein ◽  
Pathogenic Fungi ◽  
Antifungal Drugs ◽  
Cell Wall Integrity ◽  
Regulatory Function ◽  
Loss Of Function ◽  
Hsp90 Inhibition

Different signaling cascades including the Cell Wall Integrity (CWI), the High Osmolarity Glycerol (HOG) and the Ca2+/calcineurin pathways control the cell wall biosynthesis and remodeling in fungi. Pathogenic fungi, such as Aspergillus fumigatus and Candida albicans, greatly rely on these signaling circuits to cope with different sources of stress, including the cell wall stress evoked by antifungal drugs and the host’s response during infection. Hsp90 has been proposed as an important regulatory protein and an attractive target for antifungal therapy since it stabilizes major effector proteins that act in the CWI, HOG and Ca2+/calcineurin pathways. Data from the human pathogen C. albicans have provided solid evidence that loss-of-function of Hsp90 impairs the evolution of resistance to azoles and echinocandin drugs. In A. fumigatus, Hsp90 is also required for cell wall integrity maintenance, reinforcing a coordinated function of the CWI pathway and this essential molecular chaperone. In this review, we focus on the current information about how Hsp90 impacts the aforementioned signaling pathways and consequently the homeostasis and maintenance of the cell wall, highlighting this cellular event as a key mechanism underlying antifungal therapy based on Hsp90 inhibition.

Sign in / Sign up

Export Citation Format

Share Document