Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.4.2.30 (PARP)
13,611 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the endogenous GTP-dependent ADP-ribosylation of the alpha-subunit of the stimulatory guanyl-nucleotide-binding protein (Gs alpha) concomitant with an increase of basal adenylyl cyclase activity in chicken spleen cell membranes. When these membranes were incubated with [adenylate-32P]NAD, there was significant incorporation of [32P]ADP-ribose into a 45-kDa acceptor protein in the membranes. This reaction was inhibited when 20 mM arginine was present during the incubation. When the membranes were incubated with unlabelled NAD, subsequent ADP ribosylation by cholera toxin was diminished significantly. Thus, chicken spleen cell membranes have the potential to endogenously ADP-ribosylate the arginine residue of Gs alpha. The endogenous ADP-ribosylation Gs alpha was enhanced by the addition of 0.1 mM GTP or 0.1 mM guanosine 5'-[gamma-thio]triphosphate (GTP[S]), but not 0.1 mM GDP, 0.1 mM ATP or 0.1 mM ADP. The endogenous GTP-dependent ADP-ribosylation of Gs alpha stimulated basal adenylyl cyclase activity. Furthermore, NAD-induced stimulation of basal adenylyl cyclase activity was suppressed, when the membranes were incubated with NAD in the presence of novobiocin, an inhibitor of arginine-specific ADP-ribosyltransferase. These data represent the first demonstration that a eukaryotic cell membrane contains an ADP-ribosyltransferase which can catalyze the endogenous GTP-dependent ADP-ribosylation of the arginine residue of Gs alpha and that this modification enhances basal adenylyl cyclase activity in the membrane. In light of this evidence, the possible control of basal adenylyl cyclase activity via endogenous GTP-dependent ADP-ribosylation in eukaryotic cells warrants further attention.
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PMID:Evidence for the endogenous GTP-dependent ADP-ribosylation of the alpha-subunit of the stimulatory guanyl-nucleotide-binding protein concomitant with an increase in basal adenylyl cyclase activity in chicken spleen cell membrane. 190 78

The effects of Clostridium botulinum C3 ADP-ribosyltransferase and of Clostridium botulinum C2 toxin were studied on the cytoskeleton of rat hepatoma FAO and human glioma U333 cells. After treatment of these cells for 24 to 48 h with C3 (3-30 micrograms/ml), the actin microfilaments disappeared, and the intermediate filament network was found to collapse, while microtubules remained intact. Similar alterations of the cytoskeletal filaments without affecting microtubules were induced by the actin-ADP-ribosylating C2 toxin. In FAO cells, C3 caused the rounding up of cells. Concomitantly, cytosolic 22 to 24 kDa proteins were ADP-ribosylated in a guanine nucleotide-dependent manner. Rounding up of cells and ADP-ribosylation of proteins in intact cells were observed at similar concentration of the transferase. These data suggest a role of the protein substrates of C3 in the regulation of the cytoskeletal integrity.
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PMID:Alteration of the cytoskeleton of mammalian cells cultured in vitro by Clostridium botulinum C2 toxin and C3 ADP-ribosyltransferase. 190 79

Previous studies of the S1 subunit of pertussis toxin, an NAD(+)-dependent ADP-ribosyltransferase, suggested that a small amino-terminal region of amino acid sequence similarity to the active fragments of both cholera toxin and Escherichia coli heat-labile enterotoxin represents a region containing critical active-site residues that might be involved in the binding of the substrate NAD+. Other studies of two other bacterial toxins possessing ADP-ribosyltransferase activity, diphtheria toxin and Pseudomonas exotoxin A, have revealed the presence of essential glutamic acid residues vicinal to the active site. To help determine the relevance of these observations to activities of the enterotoxins, the A-subunit gene of the E. coli heat-labile enterotoxin was subjected to site-specific mutagenesis in the region encoding the amino-terminal region of similarity to the S1 subunit of pertussis toxin delineated by residues 6 through 17 and at two glutamic acid residues, 110 and 112, that are conserved in the active domains of all of the heat-labile enterotoxin variants and in cholera toxin. Mutant proteins in which arginine 7 was either deleted or replaced with lysine exhibited undetectable levels of ADP-ribosyltransferase activity. However, limited trypsinolysis of the arginine 7 mutants yielded fragmentation kinetics that were different from that yielded by the wild-type recombinant subunit or the authentic A subunit. In contrast, mutant proteins in which glutamic acid residues at either position 110 or 112 were replaced with aspartic acid responded like the wild-type subunit upon limited trypsinolysis, while exhibiting severely depressed, but detectable, ADP-ribosyltransferase activity. The latter results may indicate that either glutamic acid 110 or glutamic acid 112 of the A subunit of heat-labile enterotoxin is analogous to those active-site glutamic acids identified in several other ADP-ribosylating toxins.
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PMID:Effect of site-directed mutagenic alterations on ADP-ribosyltransferase activity of the A subunit of Escherichia coli heat-labile enterotoxin. 190 25

Pertussis toxin (PT) has previously been shown to affect a wide variety of immune responses and to cause lymphocyte proliferation. We have investigated the biochemical basis for the mitogenic activity of PT by using human peripheral blood lymphocytes. PT was found to induce a rapid rise in cytosolic free calcium concentration and an alkalinization of the cytosol through the Na+/H+ antiporter. The toxin was also found to induce expression of IL-2-receptor on CD3+ cells and to stimulate IL-2 production. PT induced proliferation of both CD4+ and CD8+ T cells in the presence (but not in the absence) of accessory cells. PT also stimulated IL-1 production by monocytes but neither IL-1, IL-6 alone nor a combination of the two lymphokines could replace accessory cells suggesting that cell:cell contact is required. Low doses of PT induced ADP-ribosylation of G proteins but this treatment did not affect significantly PHA-induced [Ca2+]i increase and IL-2-induced DNA synthesis suggesting that the substrates of the ADP-ribosyltransferase activity of PT are not involved in the signalling pathways leading to DNA replication.
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PMID:Pertussis toxin-induced mitogenesis in human T lymphocytes. 190 37

A GTP-binding protein with an Mr of 24,000 was purified from a cholate extract of bovine brain membranes in addition to the previously reported alpha beta gamma-trimeric GTP-binding proteins (G proteins). Partial amino acid sequence analysis of the purified 24-kDa protein revealed that it was not identical to any of the low Mr GTP-binding proteins already reported, but similar to the rac-gene products serving as the substrate of an ADP-ribosyltransferase (C3) purified from the culture medium of Clostridium botulinum type C. However, the 24-kDa protein was not ADP-ribosylated by the botulinum C3 enzyme. The 24-kDa protein was purified as a nucleotide-free form and characterized by the following unique properties distinct from those of alpha beta gamma-trimeric G proteins. (1) Mg2+ was essentially required for nucleotide binding to the 24-kDa protein; there was a progressive increase in its binding affinity for nucleotides as the concentration of the divalent cation was increased. (2) Nucleotides previously bound to the 24-kDa protein were rapidly dissociated from the protein in Mg(2+)-free medium, in accord with the fact that the protein was indeed purified as a nucleotide-free form with Mg(2+)-free solutions. (3) The 24-kDa protein apparently exhibited much lower GTPase activity than do alpha beta gamma-trimeric G proteins because the product GDP was released from the 24-kDa protein in exchange for the substrate GTP only at a very low rate. Based on these findings, a possible role of the 24-kDa protein in cellular signalling is discussed in comparison with well characterized alpha beta gamma-trimeric G proteins.
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PMID:Purification and characterization of a new GTP-binding protein of Mr 24,000 in bovine brain membranes. 190 60

C3 ADP-ribosyltransferase is an exoenzyme produced by certain strains of Clostridium botulinum types C and D, which specifically ADP-ribosylates rho and rac proteins in eukaryotic cells. The enzyme was purified from a culture filtrate of C. botulinum type C strain 003-9, and the amino acid sequence from the amino-terminal Ser to Asn192 was determined by Edman degradation. Using a set of degenerate primers based on the sequence, we amplified a part of the gene for this enzyme by polymerase chain reaction. A 2.1-kilobase pair HincII fragment of C. botulinum DNA containing the whole structural gene was then identified by Southern analysis with the polymerase chain reaction product as a probe, and the complete nucleotide structure of the gene together with flanking regions was determined by cloning and DNA sequencing the HincII fragment. The gene encodes a protein of 244 amino acids with a Mr of 27,362 which begins with a putative signal peptide of 40 amino acids. Escherichia coli carrying this gene produced the active enzyme, and about 60% of it was found in the culture medium. Immunoblot analysis with antiserum against the enzyme revealed the presence of two immunoreactive proteins of 27 and 23 kDa in the cytoplasmic/membrane fraction and only the 23-kDa protein in the periplasm and the medium, suggesting that the enzyme expressed is processed in the E. coli, exported into the periplasm and released into the culture medium.
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PMID:Clostridium botulinum C3 ADP-ribosyltransferase gene. Cloning, sequencing, and expression of a functional protein in Escherichia coli. 191 48

This paper reports the presence of several G proteins and light-sensitive GTP-binding proteins in the fungus Coprinus congregatus, a filamentous eukaryote. (Mono)ADP-ribosylation experiments with crude membranes in the presence of the (poly)ADP-ribosyltransferase inhibitor, 3-amino-benzamide, resulted in the detection of a cholera toxin substrate of 52 kDa and two pertussis toxin substrates, 33 and 39 kDa. Two-dimensional polyacrylamide gel analysis of GTP-binding proteins exposed in vivo to [35S]-labeled guanosine 5'-[gamma-thio]-triphosphate in the presence or absence of light demonstrated light enhanced analog binding. These results support the concept of the involvement of G proteins in phototransduction in C. congregatus.
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PMID:Signal transduction in Coprinus congregatus: evidence for the involvement of G proteins in blue light photomorphogenesis. 193 Jan 68

Reversible ADP-ribosylation of dinitrogenase reductase forms the basis of posttranslational regulation of nitrogenase activity in Rhodospirillum rubrum. This report describes the physiological effects of mutations in the genes encoding the enzymes that add and remove the ADP-ribosyl moiety. Mutants lacking a functional draT gene had no dinitrogenase reductase ADP-ribosyltransferase (DRAT, the draT gene product) activity in vitro and were incapable of modifying dinitrogenase reductase with ADP-ribose in vivo. Mutants lacking a functional draG gene had no dinitrogenase reductase-activating glycohydrolase (DRAG, the draG gene product) activity in vitro and were unable to remove ADP-ribose from the modified dinitrogenase reductase in vivo. Strains containing polar mutations in draT had no detectable DRAG activity in vitro, suggesting likely cotranscription of draT and draG. In strains containing draT and lacking a functional draG, dinitrogenase reductase accumulated in the active form under derepressing conditions but was rapidly ADP-ribosylated in response to conditions that cause inactivation. Detection of DRAT in these cells in vitro demonstrated that DRAT is itself subject to posttranslational regulation in vivo. Mutants affected in an open reading frame immediately downstream of draTG showed regulation of dinitrogenase reductase by ADP-ribosylation, although differences in the rates of ADP-ribosylation were apparent.
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PMID:Mutations in the draT and draG genes of Rhodospirillum rubrum result in loss of regulation of nitrogenase by reversible ADP-ribosylation. 193 94

In the pig heart sarcolemma, a 65 kDa protein is found to be ADP-ribosylated by Clostridium botulinum ADP-ribosyltransferase (exoenzyme C3). ADP-ribosylation of this protein is regulated by guanyl nucleotides and cytosol factor in a fashion similar to that for other C3 substrates. The new exoenzyme C3 substrate was partially purified. This protein is supposed to be a GTP-binding one.
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PMID:The 65-kDa protein from pig heart. A new substrate for Clostridium botulinum ADP-ribosyltransferase (exoenzyme C3). 195 72

ADP-ribosyltransferase from Clostridium botulinum type C strain was found to induce an increase of inositol phosphates (IPs) formation in murine thymocytes membranes. Incubation of electropermeabilized murine thymocytes with the enzyme also caused an increase of IPs formation in the cells. This increase of IPs formation in the enzyme-treated membranes and electropermeabilized cells was dependent on the amount of both NAD and the enzyme, suggesting that the stimulation of phosphoinositide-specific phospholipase C (PLC) was related to ADP-ribosylation of membrane proteins by the enzyme. On the other hand, in calf and murine thymocytes two proteins with the same molecular weight of 21,000 were found to be ADP-ribosylated by the botulinum ADP-ribosyltransferase. A minor ADP-ribosylation substrate was shown by two-dimensional polyacrylamide gel electrophoresis to be G21k, a low-molecular-weight GTP-binding protein (G protein) suggested previously by us to be involved in PLC regulation [Wang, P. et al. (1987) J. Biochem. 102, 1275-1287; (1988) 103, 137-142; and (1989) 105, 461-466], and the other major ADP-ribosylation substrate was identified as a rho A protein. Under the experimental conditions of the IPs formation study, ADP-ribosylation of both G21k and rho A proteins by botulinum ADP-ribosyltransferase in membranes and permeabilized cells was observed. These results suggest that botulinum ADP-ribosyltransferase-induced PLC stimulation in thymocytes is closely correlated with ADP-ribosylation of the low-molecular-weight G proteins.
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PMID:Low-molecular-weight GTP-binding proteins serving as ADP-ribosylation substrate for ADP-ribosyltransferase from Clostridium botulinum and their relation to phosphoinositides metabolism in thymocytes. 196 61


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