Mechanistic Studies on the Formation of Thiazolidine and Structurally Related Thiazines in a Cysteamine/2,3-Butanedione Model System

1998 ◽  
Vol 46 (2) ◽  
pp. 664-667 ◽  
Author(s):  
Tzou-Chi Huang ◽  
Yu-Ming Su ◽  
Chi-Tang Ho
Keyword(s):  
Model System ◽  
Mechanistic Studies

scholarly journals ORF4 of the Temperate Archaeal Virus SNJ1 Governs the Lysis-Lysogeny Switch and Superinfection Immunity

2020 ◽  
Vol 94 (16) ◽  
Author(s):  
Beibei Chen ◽  
Zhao Chen ◽  
Yuchen Wang ◽  
Han Gong ◽  
Linshan Sima ◽  
...  
Keyword(s):  
Life Cycle ◽  
Bioinformatic Analysis ◽  
Model System ◽  
Life Cycles ◽  
Host Cells ◽  
Biological Functions ◽  
Mechanistic Studies ◽  
Cultivation Conditions ◽  
Archaeal Virus ◽  
Archaeal Viruses

ABSTRACT Recent environmental and metagenomic studies have considerably increased the repertoire of archaeal viruses and suggested that they play important roles in nutrient cycling in the biosphere. However, very little is known about how they regulate their life cycles and interact with their hosts. Here, we report that the life cycle of the temperate haloarchaeal virus SNJ1 is controlled by the product ORF4, a small protein belonging to the antitoxin MazE superfamily. We show that ORF4 controls the lysis-lysogeny switch of SNJ1 and mediates superinfection immunity by repression of genomic DNA replication of the superinfecting viruses. Bioinformatic analysis shows that ORF4 is highly conserved in two SNJ1-like proviruses, suggesting that the mechanisms for lysis-lysogeny switch and superinfection immunity are conserved in this group of viruses. As the lysis-lysogeny switch and superinfection immunity of archaeal viruses have been poorly studied, we suggest that SNJ1 could serve as a model system to study these processes. IMPORTANCE Archaeal viruses are important parts of the virosphere. Understanding how they regulate their life cycles and interact with host cells provide crucial insights into their biological functions and the evolutionary histories of viruses. However, mechanistic studies of the life cycle of archaeal viruses are scarce due to a lack of genetic tools and demanding cultivation conditions. Here, we discover that the temperate haloarchaeal virus SNJ1, which infects Natrinema sp. strain J7, employs a lysis-lysogeny switch and establishes superinfection immunity like bacteriophages. We show that its ORF4 is critical for both processes and acts as a repressor of the replication of SNJ1. These results establish ORF4 as a master regulator of SNJ1 life cycle and provides novel insights on the regulation of life cycles by temperate archaeal viruses and on their interactions with host cells.

Model system-based mechanistic studies of black tea thearubigin formation

2015 ◽  
Vol 180 ◽  
pp. 272-279 ◽  
Author(s):  
Ghada H. Yassin ◽  
Jan H. Koek ◽  
Nikolai Kuhnert
Keyword(s):  
Black Tea ◽  
Model System ◽  
Mechanistic Studies

scholarly journals Multiplexed Competition in a Synthetic Squid Light Organ Microbiome Using Barcode-Tagged Gene Deletions

mSystems ◽  
2020 ◽  
Vol 5 (6) ◽  
pp. e00846-20
Author(s):  
Hector L. Burgos ◽  
Emanuel F. Burgos ◽  
Andrew J. Steinberger ◽  
Garret Suen ◽  
Mark J. Mandel
Keyword(s):  
Vibrio Fischeri ◽  
Bacterial Genome ◽  
Model System ◽  
Mechanistic Studies ◽  
Gene Deletions ◽  
Content Type ◽  
Animal Host ◽  
Overlap Extension ◽  
Health And Development ◽  
Colonization Factors

ABSTRACTBeneficial symbioses between microbes and their eukaryotic hosts are ubiquitous and have widespread impacts on host health and development. The binary symbiosis between the bioluminescent bacterium Vibrio fischeri and its squid host Euprymna scolopes serves as a model system to study molecular mechanisms at the microbe-animal interface. To identify colonization factors in this system, our lab previously conducted a global transposon insertion sequencing (INSeq) screen and identified over 300 putative novel squid colonization factors in V. fischeri. To pursue mechanistic studies on these candidate genes, we present an approach to quickly generate barcode-tagged gene deletions and perform high-throughput squid competition experiments with detection of the proportion of each strain in the mixture by barcode sequencing (BarSeq). Our deletion approach improves on previous techniques based on splicing by overlap extension PCR (SOE-PCR) and tfoX-based natural transformation by incorporating a randomized barcode that results in unique DNA sequences within each deletion scar. Amplicon sequencing of the pool of barcoded strains before and after colonization faithfully reports on known colonization factors and provides increased sensitivity over colony counting methods. BarSeq enables rapid and sensitive characterization of the molecular factors involved in establishing the Vibrio-squid symbiosis and provides a valuable tool to interrogate the molecular dialogue at microbe-animal host interfaces.IMPORTANCE Beneficial microbes play essential roles in the health and development of their hosts. However, the complexity of animal microbiomes and general genetic intractability of their symbionts have made it difficult to study the coevolved mechanisms for establishing and maintaining specificity at the microbe-animal host interface. Model symbioses are therefore invaluable for studying the mechanisms of beneficial microbe-host interactions. Here, we present a combined barcode-tagged deletion and BarSeq approach to interrogate the molecular dialogue that ensures specific and reproducible colonization of the Hawaiian bobtail squid by Vibrio fischeri. The ability to precisely manipulate the bacterial genome, combined with multiplex colonization assays, will accelerate the use of this valuable model system for mechanistic studies of how environmental microbes—both beneficial and pathogenic—colonize specific animal hosts.

The Possible Use of Isolated Human Platelets in In Vitro Cell Toxicology

1992 ◽  
Vol 20 (2) ◽  
pp. 258-261
Author(s):  
Jan-Henrik Mäkelä ◽  
Boris Isomaa
Keyword(s):  
Protein Kinase C ◽  
Human Platelet ◽  
Specific Inhibitor ◽  
Human Platelets ◽  
Model System ◽  
Mechanistic Studies ◽  
Short Term ◽  
Kinase C ◽  
Cytotoxic Compounds

Isolated human platelets represent a model system which could be used in in vitro cell toxicology for mechanistic studies on the short-term effects of cytotoxic compounds. We have recorded changes in the concentration of free cytosolic Ca2+ ([Ca2+]i) with Fura 2 in isolated human platelets treated with sphingosine, a compound suggested to be a specific inhibitor of protein kinase C (PKC). We huve shown that sphingosine is able to induce a rapid and transient release of Ca2+ from the intracellular stores in platelets. Furthermore, a massive efflux of released Ca2+ was shown. These effects of sphingosine on the human platelet might leave the cell incapable of performing Ca2+-dependent reactions, including PKC-mediated phosphorylation, upon stimulation subsequent to sphingosine-treatment.

Mechanistic studies on the enzymatic processing of fluorinated methionine analogues by Trichomonas vaginalis methionine γ-lyase

2011 ◽  
Vol 438 (3) ◽  
pp. 513-521 ◽  
Author(s):  
Ignace A. Moya ◽  
Gareth D. Westrop ◽  
Graham H. Coombs ◽  
John F. Honek
Keyword(s):  
Trichomonas Vaginalis ◽  
Chemical Structure ◽  
Pyridoxal Phosphate ◽  
Model System ◽  
Methyl Mercaptan ◽  
Human Pathogen ◽  
Human Pathogens ◽  
Mechanistic Studies ◽  
Cellular Toxicity ◽  
The Relationship

TFM (L-trifluoromethionine), a potential prodrug, was reported to be toxic towards human pathogens that express MGL (L-methionine γ-lyase; EC 4.4.1.11), a pyridoxal phosphate-containing enzyme that converts L-methionine into α-oxobutyrate, ammonia and methyl mercaptan. It has been hypothesized that the extremely reactive thiocarbonyl difluoride is produced when the enzyme acts upon TFM, resulting in cellular toxicity. The potential application of the fluorinated thiomethyl group in other areas of biochemistry and medicinal chemistry requires additional studies. Therefore a detailed investigation of the theoretical and experimental chemistry and biochemistry of these fluorinated groups (CF3S− and CF2HS−) has been undertaken to trap and identify chemical intermediates produced by enzyme processing of molecules containing these fluorinated moieties. TvMGL (MGL from Trichomonas vaginalis) and a chemical model system of the reaction were utilized in order to investigate the cofactor-dependent activation of TFM and previously uninvestigated DFM (L-difluoromethionine). The differences in toxicity between TFM and DFM were evaluated against Escherichia coli expressing TvMGL1, as well as the intact human pathogen T. vaginalis. The relationship between the chemical structure of the reactive intermediates produced from the enzymatic processing of these analogues and their cellular toxicity are discussed.

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