The metabolite repair enzyme Nit1 is a dual-targeted amidase that disposes of damaged glutathione in Arabidopsis

2019 ◽  
Vol 476 (4) ◽  
pp. 683-697 ◽  
Author(s):  
Thomas D. Niehaus ◽  
Jenelle A. Patterson ◽  
Danny C. Alexander ◽  
Jakob S. Folz ◽  
Michal Pyc ◽  
...  
Keyword(s):  
In Vitro Transcription ◽  
Start Codon ◽  
Repair System ◽  
Leaf Extracts ◽  
Physiological Processes ◽  
Translation Start ◽  
Targeting Peptide ◽  
Cellular Compartments ◽  
Metabolite Repair

Abstract The tripeptide glutathione (GSH) is implicated in various crucial physiological processes including redox buffering and protection against heavy metal toxicity. GSH is abundant in plants, with reported intracellular concentrations typically in the 1–10 mM range. Various aminotransferases can inadvertently transaminate the amino group of the γ-glutamyl moiety of GSH to produce deaminated glutathione (dGSH), a metabolite damage product. It was recently reported that an amidase known as Nit1 participates in dGSH breakdown in mammals and yeast. Plants have a hitherto uncharacterized homolog of the Nit1 amidase. We show that recombinant Arabidopsis Nit1 (At4g08790) has high and specific amidase activity towards dGSH. Ablating the Arabidopsis Nit1 gene causes a massive accumulation of dGSH and other marked changes to the metabolome. All plant Nit1 sequences examined had predicted plastidial targeting peptides with a potential second start codon whose use would eliminate the targeting peptide. In vitro transcription/translation assays show that both potential translation start codons in Arabidopsis Nit1 were used and confocal microscopy of Nit1–GFP fusions in plant cells confirmed both cytoplasmic and plastidial localization. Furthermore, we show that Arabidopsis enzymes present in leaf extracts convert GSH to dGSH at a rate of 2.8 pmol min−1 mg−1 in the presence of glyoxalate as an amino acceptor. Our data demonstrate that plants have a dGSH repair system that is directed to at least two cellular compartments via the use of alternative translation start sites.

scholarly journals Point-Substitution of Phenylalanine Residues of 26RFa Neuropeptide: A Structure-Activity Relationship Study

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4312
Author(s):  
Benjamin Lefranc ◽  
Karima Alim ◽  
Cindy Neveu ◽  
Olivier Le Marec ◽  
Christophe Dubessy ◽  
...  
Keyword(s):  
Receptor Activation ◽  
Pharmacological Profile ◽  
Acid Moiety ◽  
Structural Determinants ◽  
Physiological Processes ◽  
Structure Activity ◽  
Peptide Derivatives ◽  
Targeting Peptide ◽  
G Protein Coupled

26RFa is a neuropeptide that activates the rhodopsin-like G protein-coupled receptor QRFPR/GPR103. This peptidergic system is involved in the regulation of a wide array of physiological processes including feeding behavior and glucose homeostasis. Herein, the pharmacological profile of a homogenous library of QRFPR-targeting peptide derivatives was investigated in vitro on human QRFPR-transfected cells with the aim to provide possible insights into the structural determinants of the Phe residues to govern receptor activation. Our work advocates to include in next generations of 26RFa(20–26)-based QRFPR agonists effective substitutions for each Phe unit, i.e., replacement of the Phe22 residue by a constrained 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid moiety, and substitution of both Phe24 and Phe26 by their para-chloro counterpart. Taken as a whole, this study emphasizes that optimized modifications in the C-terminal part of 26RFa are mandatory to design selective and potent peptide agonists for human QRFPR.

scholarly journals Identification of an AU-rich Translational Enhancer within the Escherichia coli fepB Leader RNA

2007 ◽  
Vol 189 (11) ◽  
pp. 4028-4037 ◽  
Author(s):  
India G. Hook-Barnard ◽  
Timothy J. Brickman ◽  
Mark A. McIntosh
Keyword(s):  
Escherichia Coli ◽  
Posttranscriptional Regulation ◽  
Selective Advantage ◽  
In Vitro Transcription ◽  
Start Codon ◽  
Translational Efficiency ◽  
Rnase Protection ◽  
Ribosome Binding ◽  
Translational Enhancer

ABSTRACT The fepB gene encodes a periplasmic binding protein that is essential for the uptake of ferric enterobactin by Escherichia coli. Its transcription is regulated in response to iron levels by the Fur repressor. The fepB transcript includes a 217-nucleotide leader sequence with several features suggestive of posttranscriptional regulation. To investigate the fepB leader for its contribution to fepB expression, defined deletions and substitution mutations in the leader were characterized using fepB-phoA translational fusions. The fepB leader was found to be necessary for maximal fepB expression, primarily due to the influence of an AU-rich translational enhancer (TE) located 5′ to the Shine-Dalgarno sequence. Deletions or substitutions within the TE sequence decreased fepB-phoA expression fivefold. RNase protection and in vitro transcription-translation assays demonstrated that the TE augmented translational efficiency, as well as RNA levels. Moreover, primer extension inhibition assays showed that the TE increases ribosome binding. In contrast to the enhancing effect of the TE, the natural fepB GUG start codon decreased ribosome binding and reduced fepB expression 2.5-fold compared with the results obtained with leaders bearing an AUG initiation codon. Thus, the TE-GUG organization in fepB results in an intermediate level of expression compared to the level with AUG, with or without the TE. Furthermore, we found that the TE-GUG sequence is conserved among the eight gram-negative strains examined that have fepB genes, suggesting that this organization may provide a selective advantage.

scholarly journals NAD(P)HX repair deficiency causes central metabolic perturbations in yeast and human cells

2018 ◽  
Author(s):  
Julia Becker-Kettern ◽  
Nicole Paczia ◽  
Jean-François Conrotte ◽  
Chenchen Zhu ◽  
Oliver Fiehn ◽  
...  
Keyword(s):  
Cell Metabolism ◽  
Early Death ◽  
Human Cells ◽  
Repair System ◽  
Cellular Functions ◽  
Repair Deficiency ◽  
Domains Of Life ◽  
Metabolite Repair

ABSTRACTNADHX and NADPHX are hydrated and redox inactive forms of the NADH and NADPH cofactors, known to inhibit several dehydrogenasesin vitro. A metabolite repair system that is conserved in all domains of life and that comprises the two enzymes NAD(P)HX dehydratase and NAD(P)HX epimerase, allows reconversion of both theS- andR-epimers of NADHX and NADPHX to the normal cofactors. An inherited deficiency in this system has recently been shown to cause severe neurometabolic disease in children. Although evidence for the presence of NAD(P)HX has been obtained in plant and human cells, little is known about the mechanism of formation of these derivativesin vivoand their potential effects on cell metabolism. Here, we show that NAD(P)HX dehydratase deficiency in yeast leads to an important, temperature-dependent NADHX accumulation in quiescent cells with a concomitant depletion of intracellular NAD+and serine pools. We demonstrate that NADHX potently inhibits the first step of the serine synthesis pathway in yeast. Human cells deficient in the NAD(P)HX dehydratase also accumulated NADHX and showed decreased viability. In addition, those cells consumed more glucose and produced more lactate, potentially indicating impaired mitochondrial function. Our results provide first insights into how NADHX accumulation affects cellular functions and pave the way for a better understanding of the mechanism(s) underlying the rapid and severe neurodegeneration leading to early death in NADHX repair deficient children.

RNA—protein interactions in the 5′ untranslated region of preproinsulin mRNA

1992 ◽  
Vol 8 (3) ◽  
pp. 225-234 ◽  
Author(s):  
S. W. Knight ◽  
K. Docherty
Keyword(s):  
Protein Interactions ◽  
Untranslated Region ◽  
In Vitro Transcription ◽  
Specific Protein ◽  
Start Codon ◽  
Mobility Shift ◽  
Stem Loop ◽  
Stem Loop Structure ◽  
Rna Probes

ABSTRACT A comparison between species of the 5′ untranslated region of preproinsulin mRNA revealed conserved sequences associated with a potential stem—loop structure. The present study was undertaken to determine whether specific protein interactions exist with mRNA sequences involved in the formation or stabilization of this structure in the 5′ untranslated region. 32P-Labelled RNA probes corresponding to sequences from this region were synthesized by an in-vitro transcription reaction and used in electrophoretic mobility shift and u.v.-crosslinking studies with cytoplasmic protein extracts from a number of cell lines. Specific protein—RNA interactions were mapped to a sequence located between nucleotides –21 and –50 upstream of the AUG start codon. A number of proteins of molecular mass 25kDa, 40kDa, 46kDa, 58kDa, 69kDa, 97kDa, 110kDa and 160kDa were specifically crosslinked to this sequence. The observed specific protein—RNA interactions in the 5′ untranslated region may affect the activity of preproinsulin mRNA.

Crystal structures of plant inorganic pyrophosphatase, an enzyme with a moonlighting autoproteolytic activity

2019 ◽  
Vol 476 (16) ◽  
pp. 2297-2319 ◽  
Author(s):  
Marta Grzechowiak ◽  
Milosz Ruszkowski ◽  
Joanna Sliwiak ◽  
Kamil Szpotkowski ◽  
Michal Sikorski ◽  
...  
Keyword(s):  
Site Directed Mutagenesis ◽  
Size Exclusion ◽  
Inorganic Pyrophosphatase ◽  
Prolonged Storage ◽  
Mitochondrial Targeting ◽  
Cleavage Rate ◽  
Inorganic Pyrophosphate ◽  
Putative Signal Peptide ◽  
Targeting Peptide

Abstract Inorganic pyrophosphatases (PPases, EC 3.6.1.1), which hydrolyze inorganic pyrophosphate to phosphate in the presence of divalent metal cations, play a key role in maintaining phosphorus homeostasis in cells. DNA coding inorganic pyrophosphatases from Arabidopsis thaliana (AtPPA1) and Medicago truncatula (MtPPA1) were cloned into a bacterial expression vector and the proteins were produced in Escherichia coli cells and crystallized. In terms of their subunit fold, AtPPA1 and MtPPA1 are reminiscent of other members of Family I soluble pyrophosphatases from bacteria and yeast. Like their bacterial orthologs, both plant PPases form hexamers, as confirmed in solution by multi-angle light scattering and size-exclusion chromatography. This is in contrast with the fungal counterparts, which are dimeric. Unexpectedly, the crystallized AtPPA1 and MtPPA1 proteins lack ∼30 amino acid residues at their N-termini, as independently confirmed by chemical sequencing. In vitro, self-cleavage of the recombinant proteins is observed after prolonged storage or during crystallization. The cleaved fragment corresponds to a putative signal peptide of mitochondrial targeting, with a predicted cleavage site at Val31–Ala32. Site-directed mutagenesis shows that mutations of the key active site Asp residues dramatically reduce the cleavage rate, which suggests a moonlighting proteolytic activity. Moreover, the discovery of autoproteolytic cleavage of a mitochondrial targeting peptide would change our perception of this signaling process.

Phytochemical analysis and salivary amylase inhibition activities of Carica papaya leaf and Garcinia mangostana pericarp extracts and partially purified fractions

2017 ◽  
Vol 6 (1) ◽  
pp. 34
Author(s):  
Michael Russelle Alvarez ◽  
Paolo Robert Bueno ◽  
Raymond Oliver Cruz ◽  
Richard Macapulay ◽  
Francis Jayson Vallesfin ◽  
...  
Keyword(s):  
Crude Extract ◽  
Carica Papaya ◽  
Uv Light ◽  
Digestive Enzyme ◽  
Phytochemical Analysis ◽  
Phytochemical Screening ◽  
Salivary Amylase ◽  
Garcinia Mangostana ◽  
Leaf Extracts

Plant-derived digestive enzyme inhibitors particularly those targeted to carbohydrate metabolism has been the focus of recent studies as natural supplements for weight control and diabetes. The present study explores the salivary amylase inhibition activity of Garcinia mangostana (Linn.) pericarp extracts and Carica papaya (Linn.) leaf extracts and fractions, as well as perform phytochemical screening and quantification, and thin layer – and high performance liquid chromatographic profiling. ­Results show that crude extracts and purified fractions were able to inhibit salivary amylase, with C. papaya fraction 1 being the most active at 30.89% inhibition. Phytochemical screening of all extracts tested ­positive for tannins, glycosides, phenolics, flavonoids and alkaloids. Quantification of phenolics showed that extracts contained high levels of phenolics, with C. papaya crude extract having the highest content with 219.0±12.7 mg GAE/g extract followed by G. mangostana crude extract with 247.1±18.0 mg GAE/g extract. Quantification of total flavonoids also showed C. papaya crude extract to contain the highest content with 55.12±0.679 mg QE/g extract. All extracts contained negligible alkaloid content, though. HPLC and TLC profiling showed several peaks and bands, when viewed in 210 nm and UV light, respectively. These results demonstrate in vitro the salivary amylase inhibitory activity of both plants and their potential as antidiabetic drug candidates; however, further studies need to be done, like isolation and structure elucidation of active components and toxicity assays. Keywords: Amylase inhibition, phytochemical quantification, Carica papaya, Garcinia mangostana

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