Publications by authors named "Samir El Qaidi"

In Escherichia coli, the master transcription regulator catabolite repressor activator (Cra) regulates >100 genes in central metabolism. Cra binding to DNA is allosterically regulated by binding to fructose-1-phosphate (F-1-P), but the only documented source of F-1-P is from the concurrent import and phosphorylation of exogenous fructose. Thus, many have proposed that fructose-1,6-bisphosphate (F-1,6-BP) is also a physiological regulatory ligand.

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Pseudogenes are defined as "non-functional" copies of corresponding parent genes. The cognition of pseudogenes continues to be refreshed through accumulating and updating research findings. Previous studies have predominantly focused on mammals, but pseudogenes have received relatively less attention in the field of microbiology.

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In , the master transcription regulator Catabolite Repressor Activator (Cra) regulates >100 genes in central metabolism. Cra binding to DNA is allosterically regulated by binding to fructose-1-phosphate (F-1-P), but the only documented source of F-1-P is from the concurrent import and phosphorylation of exogenous fructose. Thus, many have proposed that fructose-1,6-bisphosphate (F-1,6-BP) is also a physiological regulatory ligand.

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Type III secretion system (T3SS) effector proteins are primarily recognized for binding host proteins to subvert host immune response during infection. Besides their known host target proteins, several T3SS effectors also interact with endogenous bacterial proteins. Here we demonstrate that the Salmonella T3SS effector glycosyltransferase SseK1 glycosylates the bacterial two-component response regulator OmpR on two arginine residues, R15 and R122.

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The Salmonella enterica SseK1 protein is a type three secretion system effector that glycosylates host proteins during infection on specific arginine residues with N-acetyl glucosamine (GlcNAc). SseK1 also Arg-glycosylates endogenous bacterial proteins and we thus hypothesized that SseK1 activities might be integrated with regulating the intrabacterial abundance of UPD-GlcNAc, the sugar-nucleotide donor used by this effector. After searching for new SseK1 substrates, we found that SseK1 glycosylates arginine residues in the dual repressor-activator protein NagC, leading to increased DNA-binding affinity and enhanced expression of the NagC-regulated genes glmU and glmS.

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We are interested in identifying and characterizing small molecule inhibitors of bacterial virulence factors for their potential use as anti-virulence inhibitors. We identified from high-throughput screening assays a potential activity for avasimibe, a previously characterized acyl-coenzyme A: cholesterol acyltransferase inhibitor, in inhibiting the NleB and SseK arginine glycosyltransferases from Escherichia coli and Salmonella enterica, respectively. Avasimibe inhibited the activity of the Citrobacter rodentium NleB, E.

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NleB/SseK effectors are arginine-GlcNAc-transferases expressed by enteric bacterial pathogens that modify host cell proteins to disrupt signaling pathways. While the conserved NleB and NleB1 proteins display a broad selectivity towards host proteins, SseK1, SseK2, and SseK3 have a narrowed protein substrate selectivity. Here, by combining computational and biophysical experiments, we demonstrate that the broad protein substrate selectivity of NleB relies on Tyr284, a second-shell residue contiguous to the catalytic machinery.

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Whether type III secretion system (T3SS) effector proteins encoded by Gram-negative bacterial pathogens have intra-bacterial activities is an important and emerging area of investigation. Gram-negative bacteria interact with their mammalian hosts by using secretion systems to inject virulence proteins directly into infected host cells. Many of these injected protein effectors are enzymes that modify the structure and inhibit the function of mammalian proteins.

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The type III secretion system effector proteins NleB and SseK are glycosyltransferases that glycosylate protein substrates on arginine residues. We conducted high-throughput screening assays on 42,498 compounds to identify NleB/SseK inhibitors. Such small molecules may be useful as mechanistic probes and may have utility in the eventual development of anti-virulence therapies against enteric bacterial pathogens.

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Type III secretion system effector proteins have primarily been characterized for their interactions with host cell proteins and their ability to disrupt host signaling pathways. We are testing the hypothesis that some effectors are active within the bacterium, where they modulate bacterial signal transduction and physiology. We previously determined that the Citrobacter rodentium effector NleB possesses an intra-bacterial glycosyltransferase activity that increases glutathione synthetase activity to protect the bacterium from oxidative stress.

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Article Synopsis
  • The study developed a method to detect all types of Salmonella by targeting a specific region of the flgE gene, which encodes a protein related to their flagella.
  • Researchers found that even non-flagellated Salmonella species like Salmonella Gallinarum and Salmonella Pullorum possess the flgE gene, leading to the identification of two highly conserved regions within this gene.
  • The new PCR technique successfully detected Salmonella in various bacterial strains and food samples, confirming its effectiveness for identifying Salmonella in contaminated environments and clinical settings.
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Many Gram-negative bacterial pathogens interact with mammalian cells by using type III secretion systems (T3SS) to inject virulence proteins into host cells. A subset of these injected protein 'effectors' are enzymes that inhibit the function of host proteins by catalyzing the addition of unusual post-translational modifications. The E.

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DNA cloning remains the primary step before the further investigation of gene function. Restriction enzyme-based cloning methods are still widely used and numerous restriction-free cloning techniques are available as alternatives. Here we describe a PCR-based cloning method named ABC cloning.

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The enteropathogenic and enterohemorrhagic NleB proteins as well as the SseK proteins are type III secretion system effectors that function as glycosyltransferase enzymes to post-translationally modify host substrates on arginine residues. This modification is unusual because it occurs on the guanidinium groups of arginines, which are poor nucleophiles, and is distinct from the activity of the mammalian -linked -acetylglucosaminyltransferase. We conducted high-throughput screening assays to identify small molecules that inhibit NleB/SseK activity.

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Bacteria deliver virulence proteins termed 'effectors' to counteract host innate immunity. Protein-protein interactions within the host cell ultimately subvert the generation of an inflammatory response to the infecting pathogen. Here we briefly describe a subset of T3SS effectors produced by enterohemorrhagic Escherichia coli (EHEC), enteropathogenic E.

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Many Gram-negative bacterial pathogens use type III secretion systems to deliver virulence proteins (effectors) into host cells to counteract innate immunity. The ribosomal protein S3 (RPS3) guides NF-κB subunits to specific κB sites and plays an important role in the innate response to bacterial infection. Two effectors inhibit RPS3 nuclear translocation.

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The bacterial effector proteins SseK and NleB glycosylate host proteins on arginine residues, leading to reduced NF-κB-dependent responses to infection. Salmonella SseK1 and SseK2 are E. coli NleB1 orthologs that behave as NleB1-like GTs, although they differ in protein substrate specificity.

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Many Gram-negative bacterial pathogens use a syringe-like apparatus called a type III secretion system to inject virulence factors into host cells. Some of these effectors are enzymes that modify host proteins to subvert their normal functions. NleB is a glycosyltransferase that modifies host proteins with -acetyl-d-glucosamine to inhibit antibacterial and inflammatory host responses.

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Vitamin B₆ is an essential cofactor for a large number of enzymes in both prokaryotes and eukaryotes. In this study, we characterized the pyridoxal 5'-phosphate (PLP) biosynthesis pathway in Streptococcus pneumoniae. Our results revealed that S.

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Vibrio anguillarum utilizes quorum sensing to regulate stress responses required for survival in the aquatic environment. Like other Vibrio species, V. anguillarum contains the gene qrr1, which encodes the ancestral quorum regulatory RNA Qrr1, and phosphorelay quorum-sensing systems that modulate the expression of small regulatory RNAs (sRNAs) that destabilize mRNA encoding the transcriptional regulator VanT.

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The Mlc and NagC transcriptional repressors bind to similar 23-bp operators. The sequences are weakly palindromic, with just four positions totally conserved. There is no cross regulation observed between the repressors in vivo, but there are no obvious bases which could be responsible for operator site discrimination.

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