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Sui-lam Wong - One of the best experts on this subject based on the ideXlab platform.
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Mannitol-1-Phosphate Dehydrogenase (MtlD) Is Required for Mannitol and Glucitol Assimilation in Bacillus subtilis: Possible Cooperation of mtl and gut Operons
Journal of bacteriology, 2003Co-Authors: Shouji Watanabe, Sui-lam Wong, Miyuki Hamano, Hiroshi Kakeshita, Keigo Bunai, Shigeo Tojo, Hirotake Yamaguchi, Yasutaro Fujita, Kunio YamaneAbstract:We found that mannitol-1-phosphate dehydrogenase (MtlD), a component of the mannitol-specific phosphotransferase system, is required for Glucitol assimilation in addition to GutR, GutB, and GutP in Bacillus subtilis. Northern hybridization of total RNA and microarray studies of RNA from cells cultured on glucose, mannitol, and Glucitol indicated that mannitol as the sole carbon source induced hyperexpression of the mtl operon, whereas Glucitol induced both mtl and gut operons. The B. subtilis mtl operon consists of mtlA (encoding enzyme IICBAmt1) and mtlD, and its transcriptional regulator gene, mtlR, is located 14.4 kb downstream from the mtl operon on the chromosome. The mtlA, mtlD, and mtlR mutants disrupted by the introduction of the pMUTin derivatives MTLAd, MTLDd, and MTLRd, respectively, could not grow normally on either mannitol or Glucitol. However, the growth of MTLAd on Glucitol was enhanced by IPTG (isopropyl-β-d-thiogalactopyranoside). This mutant has an IPTG-inducible promoter (Pspac promoter) located in mtlA, and this site corresponds to the upstream region of mtlD. Insertion mutants of mtlD harboring the chloramphenicol resistance gene also could not grow on either mannitol or Glucitol. In contrast, an insertion mutant of mtlA could grow on Glucitol but not on mannitol in the presence or absence of IPTG. MtlR bound to the promoter region of the mtl operon but not to a DNA fragment containing the gut promoter region.
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Roles of Glucitol in the GutR mediated transcription activation process in Bacillus subtilis: Glucitol induces GutR to change its conformation and to bind ATP
The Journal of biological chemistry, 2001Co-Authors: Karen K. H. Poon, Joyce C.-l. Chu, Sui-lam WongAbstract:Abstract GutR is a 95-kDa Glucitol-dependent transcription activator that mediates the expression of theBacillus subtilis Glucitol operon. Glucitol allows GutR to bind tightly to its binding site located upstream of thegut promoter. In this study, a second functional role of Glucitol is identified. Glucitol induces GutR to change its conformation and triggers GutR to bind ATP efficiently. After sequential binding of Glucitol and ATP to GutR, GutR adopts a new conformation by forming a compact structure that is resistant to trypsin digestion. Under this condition, the ATP·glucitiol·GutR complex can dissociate slowly from the gutR-binding site (t = 274 min). Interestingly, if ATP in the ATP·glucitiol·GutR complex is replaced by ADP, GutR adopts another conformation and can dissociate from the gutR-binding site even faster (t = 82 min). In all these GutR-DNA binding studies in the presence of different ligands (Glucitol, ATP, or ADP), only the off-rate is affected. The vital role of ATP in the GutR-mediated transcription activation process is reflected by the poor transcription from the gut promoter with GutR(D285A) which has a mutation in the motif B of the putative ATP-binding site. A working model for this transcription activation process is presented.
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roles of Glucitol in the gutr mediated transcription activation process in bacillus subtilis tight binding of gutr to its binding site
Journal of Biological Chemistry, 2001Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
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Roles of Glucitol in the GutR-mediated Transcription Activation Process inBacillus subtilis: TIGHT BINDING OF GutR TO ITS BINDING SITE
The Journal of biological chemistry, 2000Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
Karen K. H. Poon - One of the best experts on this subject based on the ideXlab platform.
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Roles of Glucitol in the GutR mediated transcription activation process in Bacillus subtilis: Glucitol induces GutR to change its conformation and to bind ATP
The Journal of biological chemistry, 2001Co-Authors: Karen K. H. Poon, Joyce C.-l. Chu, Sui-lam WongAbstract:Abstract GutR is a 95-kDa Glucitol-dependent transcription activator that mediates the expression of theBacillus subtilis Glucitol operon. Glucitol allows GutR to bind tightly to its binding site located upstream of thegut promoter. In this study, a second functional role of Glucitol is identified. Glucitol induces GutR to change its conformation and triggers GutR to bind ATP efficiently. After sequential binding of Glucitol and ATP to GutR, GutR adopts a new conformation by forming a compact structure that is resistant to trypsin digestion. Under this condition, the ATP·glucitiol·GutR complex can dissociate slowly from the gutR-binding site (t = 274 min). Interestingly, if ATP in the ATP·glucitiol·GutR complex is replaced by ADP, GutR adopts another conformation and can dissociate from the gutR-binding site even faster (t = 82 min). In all these GutR-DNA binding studies in the presence of different ligands (Glucitol, ATP, or ADP), only the off-rate is affected. The vital role of ATP in the GutR-mediated transcription activation process is reflected by the poor transcription from the gut promoter with GutR(D285A) which has a mutation in the motif B of the putative ATP-binding site. A working model for this transcription activation process is presented.
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roles of Glucitol in the gutr mediated transcription activation process in bacillus subtilis tight binding of gutr to its binding site
Journal of Biological Chemistry, 2001Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
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Roles of Glucitol in the GutR-mediated Transcription Activation Process inBacillus subtilis: TIGHT BINDING OF GutR TO ITS BINDING SITE
The Journal of biological chemistry, 2000Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
Chyi-liang Chen - One of the best experts on this subject based on the ideXlab platform.
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roles of Glucitol in the gutr mediated transcription activation process in bacillus subtilis tight binding of gutr to its binding site
Journal of Biological Chemistry, 2001Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
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Roles of Glucitol in the GutR-mediated Transcription Activation Process inBacillus subtilis: TIGHT BINDING OF GutR TO ITS BINDING SITE
The Journal of biological chemistry, 2000Co-Authors: Karen K. H. Poon, Chyi-liang Chen, Sui-lam WongAbstract:Abstract Glucitol induction in Bacillus subtilis requires a transcription activator, GutR, and a sequence located upstream of the gut promoter. To understand the initial steps involved in the GutR-mediated transcription activation process and the physiological roles of Glucitol, GutR was overproduced and purified. In the absence of Glucitol, GutR exists as a monomer and binds directly to its binding site in the gut regulatory region. This binding site was mapped to a 29-base pair imperfect inverted repeat located between −78 and −50, and there is only one GutR binding site within the regulatory region. The kinetic parameters of the interaction between GutR and its binding site were monitored in real time using surface plasmon resonance. The half-life of the GutR-DNA complex in the absence of Glucitol was estimated to be 6.8 min. In contrast, in the presence of Glucitol, the half-life of the complex was extended to longer than 19 h by affecting only the off-rate but not the on-rate. This effect is Glucitol-specific. These data indicate that Glucitol binds to GutR and induces GutR to have an extremely tight binding at its binding site. The physiological relevance of this process in transcription activation is discussed.
Navindra P. Seeram - One of the best experts on this subject based on the ideXlab platform.
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structure activity related mechanistic and modeling studies of gallotannins containing a Glucitol core and α glucosidase
RSC Advances, 2015Co-Authors: Daniel B Niesen, Qiong Gu, Jun Xu, Ling Wang, Navindra P. SeeramAbstract:Gallotannins containing a Glucitol core, which are only produced by members of the maple (Acer) genus, are more potent α-glucosidase inhibitors than the clinical drug, acarbose. While this activity is influenced by the number of substituents on the Glucitol core (e.g. more galloyl groups leads to increased activity), the mechanisms of inhibitory action are not known. Herein, we investigated ligand–enzyme interactions and binding mechanisms of a series of ‘Glucitol-core containing gallotannins (GCGs)’ against the α-glucosidase enzyme. The GCGs included ginnalins A, B and C (containing two, one, and one galloyl/s, respectively), maplexin F (containing 3 galloyls) and maplexin J (containing 4 galloyls). All of the GCGs were noncompetitive inhibitors of α-glucosidase and their interactions with the enzyme were further explored using biophysical and spectroscopic measurements. Thermodynamic parameters (by isothermal titration calorimetry) revealed a 1 : 1 binding ratio between GCGs and α-glucosidase. The binding regions between the GCGs and α-glucosidase, probed by a fluorescent tag, 1,1′-bis(4-anilino-5-naphthalenesulfonic acid), revealed that the GCGs decreased the hydrophobic surface of the enzyme. In addition, circular dichroism analyses showed that the GCGs bind to α-glucosidase and lead to loss of the secondary α-helix structure of the protein. Also, molecular modeling was used to predict the binding site between the GCGs and the α-glucosidase enzyme. This is the first study to evaluate the mechanisms of inhibitory activities of gallotannins containing a Glucitol core on α-glucosidase.
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new maplexins f i and phenolic glycosides from red maple acer rubrum bark
Tetrahedron, 2012Co-Authors: Tao Yuan, Navindra P. SeeramAbstract:Abstract Four new gallotannins, maplexins F–I (1–4), two new phenolic glycosides, rubrumosides A–B (5,6), and eleven known compounds were isolated from red maple (Acer rubrum) bark. Their structures were elucidated based on spectroscopic analysis. The maplexins contained three galloylated derivatives attached to different positions of 1,5-anhydro-Glucitol and were 10–20 fold more potent α-glucosidase inhibitors than the clinical drug, Acarbose (IC50=7–16 vs 161 μM), in vitro. These results support previous data suggesting that gallotannins are the main contributors to the α-glucosidase inhibitory activities of maple plant part extracts and that three substituents on the 1,5-anhydro-Glucitol moiety are important for activity.
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Maplexins, new α-glucosidase inhibitors from red maple (Acer rubrum) stems.
Bioorganic & Medicinal Chemistry Letters, 2011Co-Authors: Tao Yuan, Liya Li, Vamsikrishna Kandhi, Nadja B. Cech, Navindra P. SeeramAbstract:Thirteen gallic acid derivatives including five new gallotannins, named maplexins A–E, were isolated from red maple (Acer rubrum) stems. The compounds were identified by spectral analyses. The maplexins varied in number and location of galloyl groups attached to 1,5-anhydro-d-Glucitol. The isolates were evaluated for a-glucosidase inhibitory and antioxidant activities. Maplexin E, the first compound identified with three galloyl groups linked to three different positions of 1,5-anhydro-d-Glucitol, was 20 fold more potent than the a-glucosidase inhibitory drug, Acarbose (IC50 = 8 vs 160 µM). Structure–activity related studies suggested that both number and position of galloyls attached to 1,5-anhydro-d-Glucitol were important for a-glucosidase inhibition.Graphical abstractThirteen gallic acid derivatives, including five new gallotannins, 2, 3, 5, 6, 9, assigned the common names of maplexins A–E, respectively, were isolated from red maple stems. The isolates were evaluated for a-glucosidase inhibitory and antioxidant activities in vitro. [The original abstract for this article contains an image that cannot be displayed here. Please click on the link below to read the full abstract and article.]
Gertwieland Kohring - One of the best experts on this subject based on the ideXlab platform.
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an l Glucitol oxidizing dehydrogenase from bradyrhizobium japonicum usda 110 for production of d sorbose with enzymatic or electrochemical cofactor regeneration
Applied Microbiology and Biotechnology, 2014Co-Authors: Sabrina Gauer, Friedrich Giffhorn, Zhijie Wang, Harm Otten, Mathieu Etienne, Morten J Bjerrum, Leila Lo Leggio, Alain Walcarius, Gertwieland KohringAbstract:A gene in Bradyrhizobium japonicum USDA 110, annotated as a ribitol dehydrogenase (RDH), had 87 % sequence identity (97 % positives) to the N-terminal 31 amino acids of an l-Glucitol dehydrogenase from Stenotrophomonas maltophilia DSMZ 14322. The 729-bp long RDH gene coded for a protein consisting of 242 amino acids with a molecular mass of 26.1 kDa. The heterologously expressed protein not only exhibited the main enantio selective activity with d-Glucitol oxidation to d-fructose but also converted l-Glucitol to d-sorbose with enzymatic cofactor regeneration and a yield of 90 %. The temperature stability and the apparent K m value for l-Glucitol oxidation let the enzyme appear as a promising subject for further improvement by enzyme evolution. We propose to rename the enzyme from the annotated RDH gene (locus tag bll6662) from B. japonicum USDA as a d-sorbitol dehydrogenase (EC 1.1.1.14).