scholarly journals The ilvGMEDA Operon Is Regulated by Transcription Attenuation in Vibrio alginolyticus ZJ-T

2019 ◽  
Vol 85 (19) ◽  
Author(s):  
Yiqin Deng ◽  
Xing Luo ◽  
Mei Xie ◽  
Philippe Bouloc ◽  
Chang Chen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Branched Chain Amino Acids ◽  
Vibrio Alginolyticus ◽  
Gram Negative ◽  
Content Type ◽  
Wide Range ◽  
Transcription Attenuation ◽  
Branched Chain ◽  
Fish And Shellfish

ABSTRACT Bacteria synthesize amino acids according to their availability in the environment or, in the case of pathogens, within the host. We explored the regulation of the biosynthesis of branched-chain amino acids (BCAAs) (l-leucine, l-valine, and l-isoleucine) in Vibrio alginolyticus, a marine fish and shellfish pathogen and an emerging opportunistic human pathogen. In this species, the ilvGMEDA operon encodes the main pathway for biosynthesis of BCAAs. Its upstream regulatory region shows no sequence similarity to the corresponding region in Escherichia coli or other Enterobacteriaceae, and yet we show that this operon is regulated by transcription attenuation. The translation of a BCAA-rich peptide encoded upstream of the structural genes provides an adaptive response similar to the E. coli canonical model. This study of a nonmodel Gram-negative organism highlights the mechanistic conservation of transcription attenuation despite the absence of primary sequence conservation. IMPORTANCE This study analyzes the regulation of the biosynthesis of branched-chain amino acids (leucine, valine, and isoleucine) in Vibrio alginolyticus, a marine bacterium that is pathogenic to fish and humans. The results highlight the conservation of the main regulatory mechanism with that of the enterobacterium Escherichia coli, suggesting that such a mechanism appeared early during the evolution of Gram-negative bacteria, allowing adaptation to a wide range of environments.

scholarly journals Basal-Level Effects of (p)ppGpp in the Absence of Branched-Chain Amino Acids in Actinobacillus pleuropneumoniae

2020 ◽  
Vol 202 (8) ◽  
Author(s):  
Gang Li ◽  
Qian Zhao ◽  
Tian Luan ◽  
Yangbo Hu ◽  
Yueling Zhang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
De Novo ◽  
Model Organism ◽  
Stringent Response ◽  
Actinobacillus Pleuropneumoniae ◽  
Branched Chain Amino Acids ◽  
Content Type ◽  
Phenotypic Differences ◽  
Branched Chain

ABSTRACT The (p)ppGpp-mediated stringent response (SR) is a highly conserved regulatory mechanism in bacterial pathogens, enabling adaptation to adverse environments, and is linked to pathogenesis. Actinobacillus pleuropneumoniae can cause damage to the lungs of pigs, its only known natural host. Pig lungs are known to have a low concentration of free branched-chain amino acids (BCAAs) compared to the level in plasma. We had investigated the role for (p)ppGpp in viability and biofilm formation of A. pleuropneumoniae. Now, we sought to determine whether (p)ppGpp was a trigger signal for the SR in A. pleuropneumoniae in the absence of BCAAs. Combining transcriptome and phenotypic analyses of the wild type (WT) and an relA spoT double mutant [which does not produce (p)ppGpp], we found that (p)ppGpp could repress de novo purine biosynthesis and activate antioxidant pathways. There was a positive correlation between GTP and endogenous hydrogen peroxide content. Furthermore, the growth, viability, morphology, and virulence were altered by the inability to produce (p)ppGpp. Genes involved in the biosynthesis of BCAAs were constitutively upregulated, regardless of the existence of BCAAs, without accumulation of (p)ppGpp beyond a basal level. Collectively, our study shows that the absence of BCAAs was not a sufficient signal to trigger the SR in A. pleuropneumoniae. (p)ppGpp-mediated regulation in A. pleuropneumoniae is different from that described for the model organism Escherichia coli. Further work will establish whether the (p)ppGpp-dependent SR mechanism in A. pleuropneumoniae is conserved among other veterinary pathogens, especially those in the Pasteurellaceae family. IMPORTANCE (p)ppGpp is a key player in reprogramming transcriptomes to respond to nutritional challenges. Here, we present transcriptional and phenotypic differences of A. pleuropneumoniae grown in different chemically defined media in the absence of (p)ppGpp. We show that the deprivation of branched-chain amino acids (BCAAs) does not elicit a change in the basal-level (p)ppGpp, but this level is sufficient to regulate the expression of BCAA biosynthesis. The mechanism found in A. pleuropneumoniae is different from that of the model organism Escherichia coli but similar to that found in some Gram-positive bacteria. This study not only broadens the research scope of (p)ppGpp but also further validates the complexity and multiplicity of (p)ppGpp regulation in microorganisms that occupy different biological niches.

scholarly journals YjeH Is a Novel Exporter of l-Methionine and Branched-Chain Amino Acids in Escherichia coli

2015 ◽  
Vol 81 (22) ◽  
pp. 7753-7766 ◽  
Author(s):  
Qian Liu ◽  
Yong Liang ◽  
Yun Zhang ◽  
Xiuling Shang ◽  
Shuwen Liu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Fluorescent Protein ◽  
Branched Chain Amino Acids ◽  
Transport Systems ◽  
Content Type ◽  
Overexpression Strain ◽  
Branched Chain ◽  
Amino Acid Efflux

ABSTRACTAmino acid efflux transport systems have important physiological functions and play vital roles in the fermentative production of amino acids. However, no methionine exporter has yet been identified inEscherichia coli. In this study, we identified a novel amino acid exporter, YjeH, inE. coli. TheyjeHoverexpression strain exhibited high tolerance to the structural analogues ofl-methionine and branched-chain amino acids, decreased intracellular amino acid levels, and enhanced export rates in the presence of a Met-Met, Leu-Leu, Ile-Ile, or Val-Val dipeptide, suggesting that YjeH functions as an exporter ofl-methionine and the three branched-chain amino acids. The export of the four amino acids in theyjeHoverexpression strain was competitively inhibited in relation to each other. The expression ofyjeHwas strongly induced by increasing cytoplasmic concentrations of substrate amino acids. Green fluorescent protein (GFP)-tagged YjeH was visualized by total internal reflection fluorescence microscopy to confirm the plasma membrane localization of YjeH. Phylogenetic analysis of transporters indicated that YjeH belongs to the amino acid efflux family of the amino acid/polyamine/organocation (APC) superfamily. Structural modeling revealed that YjeH has the typical “5 + 5” transmembrane α-helical segment (TMS) inverted-repeat fold of APC superfamily transporters, and its binding sites are strictly conserved. The enhanced capacity ofl-methionine export by the overexpression ofyjeHin anl-methionine-producing strain resulted in a 70% improvement in titer. This study supplements the transporter classification and provides a substantial basis for the application of the methionine exporter in metabolic engineering.

scholarly journals Aminotransferase Activities of Branched Chain Amino Acids in Escherichia coli.

1968 ◽  
Vol 22 ◽  
pp. 2733-2735 ◽  
Author(s):  
Raimo Raunio ◽  
Anders Måhlén ◽  
Katri Haro ◽  
Torbjörn Norin
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Branched Chain Amino Acids ◽  
Branched Chain

scholarly journals Modulation of the Sensitivity of FimB Recombination to Branched-Chain Amino Acids and Alanine in Escherichia coli K-12

2005 ◽  
Vol 187 (18) ◽  
pp. 6273-6280 ◽  
Author(s):  
Maryam Lahooti ◽  
Paula L. Roesch ◽  
Ian C. Blomfield
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Invertible Element ◽  
Regulatory Protein ◽  
Regulatory Elements ◽  
Branched Chain Amino Acids ◽  
Integration Host Factor ◽  
Control Element ◽  
Branched Chain ◽  
K 12

ABSTRACT Phase variation of type 1 fimbriae of Escherichia coli requires the site-specific recombination of a short invertible element. Inversion is catalyzed by FimB (switching in either direction) or FimE (inversion mainly from on to off) and is influenced by auxiliary factors integration host factor (IHF) and leucine-responsive regulatory protein (Lrp). These proteins bind to sites (IHF site II and Lrp sites 1 and 2) within the invertible element to stimulate recombination, presumably by bending the DNA to enhance synapses. Interaction of Lrp with a third site (site 3) cooperatively with sites 1 and 2 (termed complex 1) impedes recombination. Inversion is stimulated by the branched-chain amino acids (particularly leucine) and alanine, and according to a current model, the amino acids promote the selective loss of Lrp from site 3 (complex 2). Here we show that the central portion of the fim invertible element, situated between Lrp site 3 and IHF site II, is dispensable for FimB recombination but that this region is also required for full amino acid stimulation of inversion. Further work reveals that the region is likely to contain multiple regulatory elements. Lrp site 3 is shown to bind the regulatory protein with low affinity, and a mutation that enhances binding to this element is found both to diminish the stimulatory effects of IVLA on FimB recombination and to inhibit recombination in the absence of the amino acids. The results obtained emphasize the importance of Lrp site 3 as a control element but also highlight the complexity of the regulatory system that affects this site.

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