The Chemical Chaperone Proline Relieves the Thermosensitivity of a
            <i>dnaK</i>
            Deletion Mutant at 42°C

Chattopadhyay, M. K.; Kern, Renée; Mistou, Michel‐Yves; Dandekar, Abhaya M.; Uratsu, Sandra L.; Richarme, Gilbert

doi:10.1128/jb.186.23.8149-8152.2004

Cited by 73 publications

(62 citation statements)

References 22 publications

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“…Proline is a multifaceted amino acid with important roles in carbon and nitrogen metabolism; protein synthesis; and protection against various environmental factors such as drought (44), metal toxicity (45,46), osmotic stress (24,25), ultraviolent irradiation (47), unfolded protein stress (26,48), and oxidative stress (19,23,27,28,49). In this study, we explored the role of proline metabolism in oxidative stress protection by characterizing the oxidative stress response of wild-type and putA mutant E. coli strains.…”

Section: Discussionmentioning

confidence: 99%

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Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

2014

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The oxidation of L-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and ⌬ 1 -pyrroline-5-carboxylate (P5C) dehydrogenase domains in a single polypeptide. Previous studies have suggested that aside from providing energy, proline metabolism influences oxidative stress resistance in different organisms. To explore this potential role and the mechanism, we characterized the oxidative stress resistance of wild-type and putA mutant strains of Escherichia coli. Initial stress assays revealed that the putA mutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in the putA mutant strain restored oxidative stress resistance, confirming that depletion of PutA was responsible for the oxidative stress phenotype. Treatment of wild-type cells with proline significantly increased hydroperoxidase I (encoded by katG) expression and activity. Furthermore, the ⌬katG strain failed to respond to proline, indicating a critical role for hydroperoxidase I in the mechanism of proline protection. The global regulator OxyR activates the expression of katG along with several other genes involved in oxidative stress defense. In addition to katG, proline increased the expression of grxA (glutaredoxin 1) and trxC (thioredoxin 2) of the OxyR regulon, implicating OxyR in proline protection. Proline oxidative metabolism was shown to generate hydrogen peroxide, indicating that proline increases oxidative stress tolerance in E. coli via a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.T he conversion of L-proline to glutamate is a four-electron oxidation process that is coordinated in two successive steps by the enzymes proline dehydrogenase (PRODH) and ⌬ 1 -pyrroline-5-carboxylate dehydrogenase (P5CDH) (Fig. 1) (1). In eukaryotes, PRODH and P5CDH are separately encoded enzymes localized in the mitochondrion. In Gram-negative bacteria, PRODH and P5CDH are combined into a bifunctional enzyme known as proline utilization A (PutA) (1, 2). The PRODH domain contains a noncovalently bound flavin adenine dinucleotide (FAD) cofactor and couples the two-electron oxidation of proline to the reduction of ubiquinone in the cytoplasmic membrane (3). The product of the PRODH reaction, ⌬ 1 -pyrroline-5-carboxylate (P5C), is subsequently hydrolyzed to glutamate-␥-semialdehyde (GSA), which is then oxidized to glutamate by the NAD ϩ -dependent P5CDH domain (2). In certain Gram-negative bacteria such as Escherichia coli, PutA also has an N-terminal ribbon-helix-helix (RHH) DNA-binding domain (residues 1 to 47) (4). The RHH domain enables PutA to act as an autogenous transcriptional regulator of the putA and putP (highaffinity Na ϩ -proline transporter) genes (4). PutA represses put gene expression by binding to five operator sites in the put regulatory region (5). Transcription of the put genes is activated by proline, which causes a r...

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Section: Discussionmentioning

confidence: 99%

“…Proline is a well-known osmoprotectant (24,25), and in E. coli, proline has been described as being a thermoprotectant by diminishing protein aggregation during heat stress (26). Proline has also been found to help combat oxidative stress, a property which has been explored in eukaryotes such as fungi, plants, and animals (19,20,27,28).…”

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Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

2014

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“…Proline also has an established role in defending against various abiotic and biotic stresses with its properties as a compatible solute benefiting a broad-range of organisms [10][11][12][13][14][15][16][17][18][19][20]. Proline has been shown to diminish aggregation of the polyQ region of the huntington protein suggesting a preventive role of proline in neurodegenerative diseases [19].…”

Section: Introductionmentioning

confidence: 99%

Proline modulates the intracellular redox environment and protects mammalian cells against oxidative stress

Krishnan

Dickman

Becker³

2008

Free Radical Biology and Medicine

318

232

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The potential of proline to suppress reactive oxygen species (ROS) and apoptosis in mammalian cells was tested by manipulating intracellular proline levels exogenously and endogenously by overexpression of proline metabolic enzymes. Proline was observed to protect cells against H 2 O 2 , tert-butyl hydroperoxide and a carcinogenic oxidative stress inducer but was not effective against superoxide generators such as menadione. Oxidative stress protection by proline requires the secondary amine of the pyrrolidine ring and involves preservation of the glutathione redox environment. Overexpression of proline dehydrogenase (PRODH), a mitochondrial flavoenzyme that oxidizes proline, resulted in 6-fold lower intracellular proline content and decreased cell survival relative to control cells. Cells overexpressing PRODH were rescued by pipecolate, an analog that mimics the antioxidant properties of proline, and by tetrahydro-2-furoic acid, a specific inhibitor of PRODH. In contrast, overexpression of the proline biosynthetic enzymes Δ 1 -pyrroline-5-carboxylate (P5C) synthetase (P5CS) and P5C reductase (P5CR) resulted in 2-fold higher proline content, significantly lower ROS levels and increased cell survival relative to control cells. In different mammalian cell lines exposed to physiological H 2 O 2 levels, increased endogenous P5CS and P5CR expression was observed indicating upregulation of proline biosynthesis is an oxidative stress response.

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“…In addition to their well-studied function as osmoprotectants, compatible solutes also have protein-stabilizing properties that support the correct folding of polypeptides under denaturing conditions both in vitro and in vivo (4,25,56). They therefore also are referred to in the literature as chemical chaperones (13,15). The stabilizing effects of compatible solutes on macromolecules and biosynthetic processes probably contributes to their physiological functions as protectants against heat (13,23) and cold stress (3,22).…”

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confidence: 99%

Ectoine and Hydroxyectoine as Protectants against Osmotic and Cold Stress: Uptake through the SigB-Controlled Betaine-Choline- Carnitine Transporter-Type Carrier EctT from Virgibacillus pantothenticus

et al. 2011

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Virgibacillus pantothenticus has been shown to synthesize the compatible solute ectoine in response to high salinity or low growth temperature. We found that exogenously provided ectoine and hydroxyectoine also serve as protectants against these challenges. Transport studies with [ 14 C]ectoine revealed that both types of stress induced a high-affinity ectoine uptake activity in V. pantothenticus. By using an Escherichia coli mutant defective in osmoprotectant uptake systems, a functional complementation approach for osmostress resistance in the presence of ectoine was employed to retrieve a gene encoding an ectoine transporter from V. pantothenticus. The cloned gene (ectT) encodes a protein (EctT) that is a member of the BCCT (betaine-choline-carnitinetransporter) family of carriers. Osmoprotection assays demonstrated that the EctT carrier mediates the preferential import of ectoine and hydroxyectoine but also possesses minor uptake activities for the compatible solutes proline and glycine betaine. Northern blot analysis with RNA isolated from V. pantothenticus revealed that a rise in the external osmolality or a reduction in growth temperature strongly increased the transcription of the ectT gene. Primer extension analysis demonstrated that ectT was transcribed under these conditions from a SigB-type promoter. SigB is the master regulator of the general stress regulon of bacilli and provides protection to cells against various challenges, including high salinity and low temperature. Both the synthesis of ectoine and the EctT-mediated uptake of ectoine and hydroxyectoine are triggered by the same environmental cues, high salinity and cold stress, and thereby provide, in a concerted fashion, the protection of V. pantothenticus against these challenges.

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The Chemical Chaperone Proline Relieves the Thermosensitivity of a dnaK Deletion Mutant at 42°C

Cited by 73 publications

References 22 publications

Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

Proline modulates the intracellular redox environment and protects mammalian cells against oxidative stress

Ectoine and Hydroxyectoine as Protectants against Osmotic and Cold Stress: Uptake through the SigB-Controlled Betaine-Choline- Carnitine Transporter-Type Carrier EctT from Virgibacillus pantothenticus

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