scholarly journals Identification of three critical acidic residues of poly(ADP-ribose) glycohydrolase involved in catalysis: determining the PARG catalytic domain

2005 ◽  
Vol 388 (2) ◽  
pp. 493-500 ◽  
Author(s):  
Chandra N. PATEL ◽  
David W. KOH ◽  
Myron K. JACOBSON ◽  
Marcos A. OLIVEIRA
Keyword(s):  
Catalytic Activity ◽  
Catalytic Domain ◽  
Functional Characterization ◽  
Sequence Alignments ◽  
Inhibitor Binding ◽  
Conserved Sequence ◽  
Binding Residue ◽  
Acidic Residues ◽  
Hydrolysis Of

PARG [poly(ADP-ribose) glycohydrolase] catalyses the hydrolysis of α(1″→2′) or α(1‴→2″) O-glycosidic linkages of ADP-ribose polymers to produce free ADP-ribose. We investigated possible mechanistic similarities between PARG and glycosidases, which also cleave O-glycosidic linkages. Glycosidases typically utilize two acidic residues for catalysis, thus we targeted acidic residues within a conserved region of bovine PARG that has been shown to contain an inhibitor-binding site. The targeted glutamate and aspartate residues were changed to asparagine in order to minimize structural alterations. Mutants were purified and assayed for catalytic activity, as well as binding, to an immobilized PARG inhibitor to determine ability to recognize substrate. Our investigation revealed residues essential for PARG catalytic activity. Two adjacent glutamic acid residues are found in the conserved sequence Gln755-Glu-Glu757, and a third residue found in the conserved sequence Val737-Asp-Phe-Ala-Asn741. Our functional characterization of PARG residues, along with recent identification of an inhibitor-binding residue Tyr796 and a glycine-rich region Gly745-Gly-Gly747 important for PARG function, allowed us to define a PARG ‘signature sequence’ [vDFA-X3-GGg-X6–8-vQEEIRF-X3-PE-X14-E-X12-YTGYa], which we used to identify putative PARG sequences across a range of organisms. Sequence alignments, along with our mapping of PARG functional residues, suggest the presence of a conserved catalytic domain of approx. 185 residues which spans residues 610–795 in bovine PARG.

scholarly journals Structural and Catalytic Characterization of TsBGL, a β-Glucosidase From Thermofilum sp. ex4484_79

2021 ◽  
Vol 12 ◽  
Author(s):  
Anke Chen ◽  
Dan Wang ◽  
Rui Ji ◽  
Jixi Li ◽  
Shaohua Gu ◽  
...  
Keyword(s):  
Catalytic Domain ◽  
Specific Activity ◽  
Maximum Activity ◽  
Homologous Proteins ◽  
Glycosidic Bonds ◽  
Catalytic Sites ◽  
Potential Applications ◽  
Beta Glucosidase ◽  
Hydrolysis Of

Beta-glucosidase is an enzyme that catalyzes the hydrolysis of the glycosidic bonds of cellobiose, resulting in the production of glucose, which is an important step for the effective utilization of cellulose. In the present study, a thermostable β-glucosidase was isolated and purified from the Thermoprotei Thermofilum sp. ex4484_79 and subjected to enzymatic and structural characterization. The purified β-glucosidase (TsBGL) exhibited maximum activity at 90°C and pH 5.0 and displayed maximum specific activity of 139.2μmol/min/mgzne against p-nitrophenyl β-D-glucopyranoside (pNPGlc) and 24.3μmol/min/mgzen against cellobiose. Furthermore, TsBGL exhibited a relatively high thermostability, retaining 84 and 47% of its activity after incubation at 85°C for 1.5h and 90°C for 1.5h, respectively. The crystal structure of TsBGL was resolved at a resolution of 2.14Å, which revealed a classical (α/β)8-barrel catalytic domain. A structural comparison of TsBGL with other homologous proteins revealed that its catalytic sites included Glu210 and Glu414. We provide the molecular structure of TsBGL and the possibility of improving its characteristics for potential applications in industries.

scholarly journals Human xylosyltransferase I and N-terminal truncated forms: functional characterization of the core enzyme

2006 ◽  
Vol 394 (1) ◽  
pp. 163-171 ◽  
Author(s):  
Sandra Müller ◽  
Jennifer Disse ◽  
Manuela Schöttler ◽  
Sylvia Schön ◽  
Christian Prante ◽  
...  
Keyword(s):  
Amino Acids ◽  
Catalytic Activity ◽  
Binding Capacity ◽  
Functional Characterization ◽  
Terminal Region ◽  
Binding Motif ◽  
Heparin Binding ◽  
Loss Of Function ◽  
The Impact

Human XT-I (xylosyltransferase I; EC 2.4.2.26) initiates the biosynthesis of the glycosaminoglycan linkage region and is a diagnostic marker of an enhanced proteoglycan biosynthesis. In the present study, we have investigated mutant enzymes of human XT-I and assessed the impact of the N-terminal region on the enzymatic activity. Soluble mutant enzymes of human XT-I with deletions at the N-terminal domain were expressed in insect cells and analysed for catalytic activity. As many as 260 amino acids could be truncated at the N-terminal region of the enzyme without affecting its catalytic activity. However, truncation of 266, 272 and 273 amino acids resulted in a 70, 90 and >98% loss in catalytic activity. Interestingly, deletion of the single 12 amino acid motif G261KEAISALSRAK272 leads to a loss-of-function XT-I mutant. This is in agreement with our findings analysing the importance of the Cys residues where we have shown that C276A mutation resulted in a nearly inactive XT-I enzyme. Moreover, we investigated the location of the heparin-binding site of human XT-I using the truncated mutants. Heparin binding was observed to be slightly altered in mutants lacking 289 or 568 amino acids, but deletion of the potential heparin-binding motif P721KKVFKI727 did not lead to a loss of heparin binding capacity. The effect of heparin or UDP on the XT-I activity of all mutants was not significantly different from that of the wild-type. Our study demonstrates that over 80% of the nucleotide sequence of the XT-I-cDNA is necessary for expressing a recombinant enzyme with full catalytic activity.

scholarly journals Functional characterization of the non-catalytic ectodomains of the nucleotide pyrophosphatase/phosphodiesterase NPP1

2003 ◽  
Vol 371 (2) ◽  
pp. 321-330 ◽  
Author(s):  
Rik GIJSBERS ◽  
Hugo CEULEMANS ◽  
Mathieu BOLLEN
Keyword(s):  
Catalytic Activity ◽  
Catalytic Domain ◽  
Transmembrane Domain ◽  
Functional Characterization ◽  
Structure Stability ◽  
Subunit Structure ◽  
Terminal Domain ◽  
Nucleotide Pyrophosphatase ◽  
Domain Truncation ◽  
And Function

The ubiquitous nucleotide pyrophosphatases/phosphodiesterases NPP1–3 consist of a short intracellular N-terminal domain, a single transmembrane domain and a large extracellular part, comprising two somatomedin-B-like domains, a catalytic domain and a poorly defined C-terminal domain. We show here that the C-terminal domain of NPP1–3 is structurally related to a family of DNA/RNA non-specific endonucleases. However, none of the residues that are essential for catalysis by the endonucleases are conserved in NPP1–NPP3, suggesting that the nuclease-like domain of NPP1–3 does not represent a second catalytic domain. Truncation analysis revealed that the nuclease-like domain of NPP1 is required for protein stability, for the targeting of NPP1 to the plasma membrane and for the expression of catalytic activity. We also demonstrate that 16 conserved cysteines in the somatomedin-B-like domains of NPP1, in concert with two flanking cysteines, mediate the dimerization of NPP1. The K173Q polymorphism of NPP1, which maps to the second somatomedin-B-like domain and has been associated with the aetiology of insulin resistance, did not affect the dimerization or catalytic activity of NPP1, and did not endow NPP1 with an affinity for the insulin receptor. Our data suggest that the non-catalytic ectodomains contribute to the subunit structure, stability and function of NPP1–3.

scholarly journals Mutating His29, His125, His133 or His158 abolishes glycosylphosphatidylinositol-specific phospholipase D catalytic activity

2005 ◽  
Vol 391 (2) ◽  
pp. 285-289 ◽  
Author(s):  
Nandita S. Raikwar ◽  
Rosario F. Bowen ◽  
Mark A. Deeg
Keyword(s):  
Catalytic Activity ◽  
Phospholipase D ◽  
Catalytic Domain ◽  
Computer Modelling ◽  
Critical Role ◽  
Biochemical Properties ◽  
Catalytic Site ◽  
Wild Type ◽  
Histidine Residues ◽  
Hydrolysis Of

Glycosylphosphatidylinositol (GPI)-specific phospholipase D (GPI-PLD) specifically cleaves GPIs. This phospholipase D is a secreted protein consisting of two domains: an N-terminal catalytic domain and a predicted C-terminal β-propeller. Although the biochemical properties of GPI-PLD have been extensively studied, its catalytic site has not been identified. We hypothesized that a histidine residue(s) may play a critical role in the catalytic activity of GPI-PLD, based on the observations that (i) Zn2+, which utilizes histidine residues for binding, is required for GPI-PLD catalytic activity, (ii) a phosphohistidine intermediate is involved in phospholipase D hydrolysis of phosphatidylcholine, (iii) computer modelling suggests a catalytic site containing histidine residues, and (iv) our observation that diethyl pyrocarbonate, which modifies histidine residues, inhibits GPI-PLD catalytic activity. Individual mutation of the ten histidine residues to asparagine in the catalytic domain of murine GPI-PLD resulted in three general phenotypes: not secreted or retained (His56 or His88), secreted with catalytic activity (His34, His81, His98 or His219) and secreted without catalytic activity (His29, His125, His133 or His158). Changing His133 but not His29, His125 or His158 to Cys resulted in a mutant that retained catalytic activity, suggesting that at least His133 is involved in Zn2+ binding. His133 and His158 also retained the biochemical properties of wild-type GPI-PLD including trypsin cleavage pattern and phosphorylation by protein kinase A. Hence, His29, His125, His133 and His158 are required for GPI-PLD catalytic activity.

scholarly journals Arabidopsis thaliana β1,2-xylosyltransferase: an unusual glycosyltransferase with the potential to act at multiple stages of the plant N-glycosylation pathway

2005 ◽  
Vol 388 (2) ◽  
pp. 515-525 ◽  
Author(s):  
Peter BENCÚR ◽  
Herta STEINKELLNER ◽  
Barbara SVOBODA ◽  
Jan MUCHA ◽  
Richard STRASSER ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Substrate Specificity ◽  
Metal Ion ◽  
Catalytic Domain ◽  
Protein Characterization ◽  
Reaction Products ◽  
Glycosylation Sites ◽  
Glycosylation Pathway ◽  
Multiple Stages

XylT (β1,2-xylosyltransferase) is a unique Golgi-bound glycosyltransferase that is involved in the biosynthesis of glycoprotein-bound N-glycans in plants. To delineate the catalytic domain of XylT, a series of N-terminal deletion mutants was heterologously expressed in insect cells. Whereas the first 54 residues could be deleted without affecting the catalytic activity of the enzyme, removal of an additional five amino acids led to the formation of an inactive protein. Characterization of the N-glycosylation status of recombinant XylT revealed that all three potential N-glycosylation sites of the protein are occupied by N-linked oligosaccharides. However, an unglycosylated version of the enzyme displayed substantial catalytic activity, demonstrating that N-glycosylation is not essential for proper folding of XylT. In contrast with most other glycosyltransferases, XylT is enzymatically active in the absence of added metal ions. This feature is not due to any metal ion directly associated with the enzyme. The precise acceptor substrate specificity of XylT was assessed with several physiologically relevant compounds and the xylosylated reaction products were subsequently tested as substrates of other Golgi-resident glycosyltransferases. These experiments revealed that the substrate specificity of XylT permits the enzyme to act at multiple stages of the plant N-glycosylation pathway.

scholarly journals Structural and functional characterization of the rod outer segment membrane guanylate cyclase

1994 ◽  
Vol 302 (2) ◽  
pp. 455-461 ◽  
Author(s):  
R M Goraczniak ◽  
T Duda ◽  
A Sitaramayya ◽  
R K Sharma
Keyword(s):  
Cyclic Gmp ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Functional Characterization ◽  
Visual Signal ◽  
Membrane Guanylate Cyclase ◽  
Rod Outer Segment ◽  
Vertebrate Photoreceptor ◽  
Hydrolysis Of

In the vertebrate photoreceptor cell, rod outer segment (ROS) is the site of visual signal-transduction process, and a pivotal molecule that regulates this process is cyclic GMP. Cyclic GMP controls the cationic conductance into the ROS, and light causes a decrease in the conductance by activating hydrolysis of the cyclic nucleotide. The identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown. We now report the cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC.

scholarly journals Characterization of PPTNs, a Cyanobacterial Phosphopantetheinyl Transferase from Nodularia spumigena NSOR10

2007 ◽  
Vol 189 (8) ◽  
pp. 3133-3139 ◽  
Author(s):  
J. N. Copp ◽  
A. A. Roberts ◽  
M. A. Marahiel ◽  
B. A. Neilan
Keyword(s):  
Acyl Carrier Protein ◽  
Functional Characterization ◽  
Bioactive Metabolites ◽  
Sequence Motifs ◽  
Phosphopantetheinyl Transferase ◽  
Carrier Proteins ◽  
Nodularia Spumigena ◽  
Conserved Sequence ◽  
Wide Range

ABSTRACT The phosphopantetheinyl transferases (PPTs) are a superfamily of essential enzymes required for the synthesis of a wide range of compounds, including fatty acids, polyketides, and nonribosomal peptide metabolites. These enzymes activate carrier proteins in specific biosynthetic pathways by transfer of a phosphopantetheinyl moiety. The diverse PPT superfamily can be divided into two families based on specificity and conserved sequence motifs. The first family is typified by the Escherichia coli acyl carrier protein synthase (AcpS), which is involved in fatty acid synthesis. The prototype of the second family is the broad-substrate-range PPT Sfp, which is required for surfactin biosynthesis in Bacillus subtilis. Most cyanobacteria do not encode an AcpS-like PPT, and furthermore, some of their Sfp-like PPTs belong to a unique phylogenetic subgroup defined by the PPTs involved in heterocyst differentiation. Here, we describe the first functional characterization of a cyanobacterial PPT based on a structural analysis and subsequent functional analysis of the Nodularia spumigena NSOR10 PPT. Southern hybridizations suggested that this enzyme may be the only PPT encoded in the N. spumigena NSOR10 genome. Expression and enzyme characterization showed that this PPT was capable of modifying carrier proteins resulting from both heterocyst glycoplipid synthesis and nodularin toxin synthesis. Cyanobacteria are a unique and vast source of bioactive metabolites; therefore, an understanding of cyanobacterial PPTs is important in order to harness the biotechnological potential of cyanobacterial natural products.

scholarly journals GlcNAc De-N-Acetylase from the Hyperthermophilic ArchaeonSulfolobus solfataricus

2018 ◽  
Vol 85 (2) ◽  
Author(s):  
Roberta Iacono ◽  
Andrea Strazzulli ◽  
Luisa Maurelli ◽  
Nicola Curci ◽  
Angela Casillo ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Recombinant Enzyme ◽  
Mass Spectrometry Analysis ◽  
Genomic Context ◽  
Content Type ◽  
Spectrometry Analysis ◽  
Additional Information ◽  
The One ◽  
Hydrolysis Of

ABSTRACTSulfolobus solfataricusis an aerobic crenarchaeal hyperthermophile with optimum growth at temperatures greater than 80°C and pH 2 to 4. Within the crenarchaeal group ofSulfolobales,N-acetylglucosamine (GlcNAc) has been shown to be a component of exopolysaccharides, forming their biofilms, and of theN-glycan decorating some proteins. The metabolism of GlcNAc is still poorly understood inArchaea, and one approach to gaining additional information is through the identification and functional characterization of carbohydrate active enzymes (CAZymes) involved in the modification of GlcNAc. The screening ofS. solfataricusextracts allowed the detection of a novel α-N-acetylglucosaminidase (α-GlcNAcase) activity, which has never been identified inArchaea. Mass spectrometry analysis of the purified activity showed a protein encoded by thesso2901gene. Interestingly, the purified recombinant enzyme, which was characterized in detail, revealed a novel de-N-acetylase activity specific for GlcNAc and derivatives. Thus, assays to identify an α-GlcNAcase found a GlcNAc de-N-acetylase instead. The α-GlcNAcase activity observed inS. solfataricusextracts did occur when SSO2901 was used in combination with an α-glucosidase. Furthermore, the inspection of the genomic context and the preliminary characterization of a putative glycosyltransferase immediately upstream ofsso2901(sso2900) suggest the involvement of these enzymes in the GlcNAc metabolism inS. solfataricus.IMPORTANCEIn this study, a preliminary screening of cellular extracts ofS. solfataricusallowed the identification of an α-N-acetylglucosaminidase activity. However, the characterization of the corresponding recombinant enzyme revealed a novel GlcNAc de-N-acetylase, which, in cooperation with the α-glucosidase, catalyzed the hydrolysis of O-α-GlcNAc glycosides. In addition, we show that the product of a gene flanking the one encoding the de-N-acetylase is a putative glycosyltransferase, suggesting the involvement of the two enzymes in the metabolism of GlcNAc. The discovery and functional analysis of novel enzymatic activities involved in the modification of this essential sugar represent a powerful strategy to shed light on the physiology and metabolism ofArchaea.

scholarly journals Identification and Functional Characterization of Chicken Toll-Like Receptor 5 Reveals a Fundamental Role in the Biology of Infection with Salmonella enterica Serovar Typhimurium

2005 ◽  
Vol 73 (4) ◽  
pp. 2344-2350 ◽  
Author(s):  
Muhammad Iqbal ◽  
Victoria J. Philbin ◽  
G. S. K. Withanage ◽  
Paul Wigley ◽  
Richard K. Beal ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Functional Characterization ◽  
Systemic Infection ◽  
Structural Similarity ◽  
Conserved Sequence ◽  
Receptor Repertoire ◽  
Serovar Typhimurium ◽  
Toll Like Receptor 5

ABSTRACT Toll-like receptors (TLRs) are a major component of the pattern recognition receptor repertoire that detect invading microorganisms and direct the vertebrate immune system to eliminate infection. In chickens, the differential biology of Salmonella serovars (systemic versus gut-restricted localization) correlates with the presence or absence of flagella, a known TLR5 agonist. Chicken TLR5 (chTLR5) exhibits conserved sequence and structural similarity with mammalian TLR5 and is expressed in tissues and cell populations of immunological and stromal origin. Exposure of chTLR5+ cells to flagellin induced elevated levels of chicken interleukin-1β (chIL-1β) but little upregulation of chIL-6 mRNA. Consistent with the flagellin-TLR5 hypothesis, an aflagellar Salmonella enterica serovar Typhimurium fliM mutant exhibited an enhanced ability to establish systemic infection. During the early stages of infection, the fliM mutant induced less IL-1β mRNA and polymorphonuclear cell infiltration of the gut. Collectively, the data represent the identification and functional characterization of a nonmammalian TLR5 and indicate a role in restricting the entry of flagellated Salmonella into systemic sites of the chicken.

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