Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet-activating factor (PAF) is an unusually potent phospholipid known to be produced by neuronal cells and to modulate cerebral blood flow and metabolism. In previous studies with NCB-20 cells, we reported that PAF induced a significant mobilization of intracellular free Ca2+ ([Ca2+]i), which was inhibited by PAF antagonists. The increase was the result of release from intracellular stores and influx from extracellular sources. The present study was designed to characterize further PAF receptor-mediated cellular signal-transduction mechanisms in myo-[3H]inositol-labeled cells. PAF induced a concentration-dependent increase in phosphatidylinositol (Pl) metabolism, with EC50 values of 1.96 +/- 0.62 nM and 1.12 +/- 0.50 nM for inositol trisphosphate (IP3) and inositol monophosphate (IP1) formation, respectively (four experiments). The maximal production of IP3 and IP1 induced by 50 nM PAF was 254 +/- 34% and 178 +/- 25% over the basal, respectively (four experiments). PAF-induced Pl metabolism was concentration-dependently inhibited by the PAF antagonist BN50739, with an IC50 value of 6.48 +/- 0.52 nM (four experiments). The protein kinase C (PKC) activator phorbol 12,13-dibutyrate concentration-dependently inhibited PAF-induced Pl metabolism and [Ca2+]i mobilization in NCB-20 cells, of NCB-20 cells with pertussis toxin (PTX) resulted in a concentration-dependent inhibition of PAF-induced IP3 production and intracellular Ca2+ release, with a maximal reduction of 66.9 +/- 3.5% and 63 +/- 6.1%, respectively, at 300 ng/ml PTX. PTX in the presence of [32P]NAD specifically [32P]ADP-ribosylated a 38-kDa protein in membranes prepared from NCB-20 cells. Pretreatment of the cells with PTX resulted in a concentration-dependent inhibition of subsequent 32P-labeling of the toxin substrate in the membranes and correlated with the uncoupling of PAF-induced IP3 formation. PAF (0.01-10 nM) elicited a concentration-related stimulation in guanosine 5'-O-(3-[35S]) triphosphate ([35S]GTP gamma S) binding to G alpha i(1,2) proteins, which was inhibited by the PAF antagonist BN50739. PAF at 10 nM also increased [35S]GTP gamma S binding to G alpha s and G alpha o. PAF-evoked activation of G alpha i(1,2) and G alpha o was reduced by preincubation with PTX. Our results reveal that neuronal cells possess PAF receptors linked through guanine nucleotide-binding proteins to phospholipase C and receptor-operated Ca2+ channels that are regulated by PKC. Both PTX-sensitive and -insensitive guanine nucleotide-binding proteins appear to couple the PAF receptor to activation of phospholipase C and the increase in [Ca2+]i. These results contribute to the further understanding of the mechanisms behind PAF actions on neuronal cells.
Mol Pharmacol 1992 Feb
PMID:Platelet-activating factor stimulates phosphoinositide turnover in neurohybrid NCB-20 cells: involvement of pertussis toxin-sensitive guanine nucleotide-binding proteins and inhibition by protein kinase C. 131 8

We have previously shown that HeLa cells contain activities implicated in tRNA splicing in yeast, a ligase capable of joining tRNA half-molecules and an NAD-dependent activity capable of removing the 2'-phosphate created at the splice junction by the ligase (Zillmann, M., Gorovsky, M.A., and Phizicky, E.M. (1991) Mol. Cell. Biol. 11, 5410-5416). We show here that removal of the splice junction 2'-phosphate is, as in yeast, a 2'-phosphate-specific phosphotransfer reaction that produces the same, as yet unidentified, small molecule. This enzyme is highly specific for oligomeric substrates having internal 2'-phosphates. Oligomers bearing terminal 2'-phosphates are at least 50-fold less reactive and those bearing 5'- or 3'-terminal phosphates are at least 600-fold less reactive. The requirement for an internal 2'-phosphate can be satisfied by a substrate as small as a dimer.
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PMID:HeLa cells contain a 2'-phosphate-specific phosphotransferase similar to a yeast enzyme implicated in tRNA splicing. 131 96

The activity of pure calf-liver and Escherichia coli thioredoxin reductases decreased drastically in the presence of NADPH or NADH, while NADP+, NAD+ and oxidized E. coli thioredoxin activated both enzymes significantly, particularly the bacterial one. The loss of activity under reducing conditions was time-dependent, thus suggesting an inactivation process: in the presence of 0.24 mM NADPH the half-lives for the E. coli and calf-liver enzymes were 13.5 and 2 min, respectively. Oxidized E. coli thioredoxin fully protected both enzymes from inactivation, and also promoted their complete reactivation after only 30 min incubation at 30 degrees C. Lower but significant protection and reactivation was also observed with NADP+ and NAD+. EDTA protected thioredoxin reductase from NADPH inactivation to a great degree, thus indicating the participation of metals in the process; EGTA did not protect the enzyme from redox inactivation. Thioredoxin reductase was extensively inactivated by NADPH under aerobic and anaerobic conditions, thus excluding the participation of O2 or oxygen active species in redox inactivation. The loss of thioredoxin reductase activity promoted by NADPH was much faster and complete in the presence of NAD+ glycohydrolase, thus suggesting that inactivation was related to full reduction of the redox-active disulfide. Those results indicate that thioredoxin reductase activity can be modulated in bacteria and mammals by the redox status of NADP(H) and thioredoxin pools, in a similar way to glutathione reductase. This would considerably expand the regulatory potential of the thioredoxin-thioredoxin reductase system with the enzyme being self-regulated by its own substrate, a regulatory protein.
Mol Cell Biochem 1992 Jan 15
PMID:NADPH and oxidized thioredoxin mediate redox interconversion of calf-liver and Escherichia coli thioredoxin reductase. 131 49

A new crystal form of the hexameric NAD(+)-linked glutamate dehydrogenase (GDH) from Clostridium symbiosum has been grown using the hanging drop method of vapour diffusion. The crystals are obtained either by using high concentrations of the amino acid substrate of the enzyme, glutamate, as the precipitant or by co-crystallization from ammonium sulphate in the presence of either p-chloromercuribenzene sulphonate or potassium tetracyanoplatinate. The crystals diffract well and X-ray photographs have established that they are in the space group R32. Considerations of the values of Vm indicate that the asymmetric unit of the R32 crystals contains a single subunit. Packing considerations based on the structure of the native enzyme determined from a different crystal form suggest that the molecule must undergo a significant conformational change in order to be accommodated in the new cell. Such a conformational rearrangement may represent an important step in the catalytic cycle.
J Mol Biol 1992 Apr 20
PMID:Effect of additives on the crystallization of glutamate dehydrogenase from Clostridium symbiosum. Evidence for a ligand-induced conformational change. 134 42

A series of 2,5-bis-substituted 3,6-diaziridinyl-1,4-benzoquinones have been tested for their ability to be reduced by the two-electron NAD(P)H:(quinone acceptor) oxidoreductase [DT-diaphorase (DTD); EC 1.6.99.2]. Symmetrically alkyl-substituted carbamoyl ester analogs of 2,5-ethyl(carboethoxyamino)3,6-diaziridinyl-1,4- benzoquinone [AZQ], 3,6-diaziridinyl-1,4-benzoquinone (DZQ), and its 2,5-dimethyl derivative (MeDZQ) were tested. The rate of reduction by DTD was DZQ greater than MeDZQ greater than n-butyl- (D5) greater than sec-butyl- (D7) greater than n-propyl- (D3) greater than methyl- (D1) greater than ethyl- (AZQ) greater than i-butyl- (D6) greater than i-propyl- (D4) substituted derivatives. The hydroxyethylamino analog (BZQ) was not a substrate for DTD. The order of toxicity to HT-29 human colon carcinoma cells (at 1-log cell kill) was MeDZQ greater than DZQ greater than BZQ greater than D1 greater than D5 greater than AZQ greater than D7 greater than D3 greater than D6 greater than D4. Dicumarol, a known inhibitor of DTD, was capable of inhibiting the cytotoxicity of DZQ, MeDZQ, AZQ, D3, D4, D5, D6, and D7, with little inhibition of D1 cytotoxicity. Alkaline elution assays suggested that DZQ induced DNA strand breaks, whereas MeDZQ induced DNA interstrand crosslinks in HT-29 cells. The formation of both classes of lesions was inhibited by dicumarol. DZQ and MeDZQ were 5-6-fold less cytotoxic to the DTD-deficient BE cell line, whereas BZQ was more cytotoxic to this cell line than the HT-29 cell line. BZQ was capable of inducing dicumarol-insensitive DNA interstrand crosslinks in both cell lines. In summary, these data show a trend between the rate of reduction by DTD of an analog and its ability to induce cytotoxicity in HT-29 cells, and they support a role for DTD in the bioreductive activation of AZQ and its analogs.
Mol Pharmacol 1992 Sep
PMID:Relationship between DT-diaphorase-mediated metabolism of a series of aziridinylbenzoquinones and DNA damage and cytotoxicity. 140 4

5'-[p-(Fluorosulfonyl)benzoyl]adenosine (5'FSBA) was previously shown to be an active site-directed affinity label of rat liver NAD(P)H:quinone acceptor oxidoreductase [Mol. Pharmacol. 35:818-822 (1989)]. Our recent study revealed that menadione, the substrate of this quinone reductase, had a magnifying effect on inactivation of the enzyme by 5'-FSBA. The dissociation constant for the initial reversible enzyme-inhibitor complex was significantly lower and the rate of inactivation was increased when menadione was present during the incubation. However, [14C]5'FSBA labeling was reduced in the presence of menadione. These results are presented and a possible mechanism for the enzyme is discussed.
Mol Pharmacol 1992 Sep
PMID:Suggested mechanism for the modulation of the activity of NAD(P)H:quinone acceptor oxidoreductase (DT-diaphorase) by menadione: interpretation of the effect of menadione on 5'-[p-(Fluorosulfonyl)benzoyl]adenosine labeling of rat liver NAD(P)H:quinone acceptor oxidoreductase. 140 5

Aldehyde dehydrogenase from bovine liver mitochondria has been crystallized using the sitting drop method of vapor diffusion at 22 degrees C. The crystals formed from solutions containing, 40 mM-sodium citrate, 1 mM-NAD+ and 21% to 24% polyethylene glycol 3400 (pH 5.3 to 5.5). X-ray diffraction data collected from these crystals indicate that the crystals belong to the orthorhombic space group P2(1)2(1)2(1) with cell dimensions of a = 153.7 A, b = 159.37 A and c = 101.45 A. The crystals diffract to at least 2.9 A and a tetramer may comprise the asymmetric unit.
J Mol Biol 1992 Oct 20
PMID:Crystallization and preliminary X-ray investigation of bovine liver mitochondrial aldehyde dehydrogenase. 143 98

The dinucleotide binding beta alpha beta motif in the crystal structures of seven different enzymes has been analysed in terms of their three-dimensional structures and primary sequences. We have identified that the hydrogen bonding of the adenine ribose to the glycine-rich turn containing the fingerprint sequence GXGXXG/A occurs via a direct or indirect mechanism, depending on the nature of the fingerprint sequence but independent of coenzyme specificity. The major determinant of the type of interaction is the nature of the residue occupying the last position of the above fingerprint. In the NAD(+)-linked dehydrogenases, an acidic residue is commonly used to form important hydrogen bonds to the adenine ribose hydroxyls and, hitherto, this residue has been thought to be an indicator of NAD+ specificity. However, on the basis of the three-dimensional structure of the NAD(+)-linked glutamate dehydrogenase (GDH) from Clostridium symbiosum we have demonstrated that this residue is not a universal requirement for the construction of an NAD+ binding site. Furthermore, considerations of sequence homology unambiguously identify an equivalent acidic residue in both NADP+ and dual specificity glutamate dehydrogenases. The conservation of this residue in these enzymes, coupled to its close proximity to the 2' phosphate implied by the necessary similarity in three-dimensional structure to C. symbiosum GDH, implicates this residue in the recognition of the 2' phosphate either via water-mediated or direct hydrogen-bonding schemes. Analysis of the latter has led us to suggest that two patterns of recognition for the 2' phosphate group of NADP(+)-binding enzymes may exist, which are distinguished by the ionization state of the 2' phosphate.
J Mol Biol 1992 Nov 20
PMID:Structural consequences of sequence patterns in the fingerprint region of the nucleotide binding fold. Implications for nucleotide specificity. 145 69

The narrow host range bacterial strain Azorhizobium caulinodans ORS571 induces the formation of nitrogen-fixing nodules on the root and stem of the tropical legume Sesbania rostrata. Here, a new flavonoid-inducible locus of ORS571 is described, locus 4. The locus was identified and isolated via the occurrence of particular sequences, the gamma and delta elements. These elements are reiterated in the ORS571 genome, linked to symbiotic loci. Sequencing of locus 4 showed the presence of an open reading frame (ORF6) that is flanked downstream by a gamma element and upstream by a delta element. The gamma element is approximately 180 bp in size, and shows homology to the insertion element ISRm3, an insertion sequence belonging to a distinct class of IS elements. The delta element is about 300 bp in size and has homology with repeated sequences found in other Rhizobiaceae. The ORF6 gene product shows a low, but significant homology to the mouse mastocytoma antigen P35B (Szikora et al., EMBO J. 9: 1041-1050, 1990) and to a class of NAD/NADP-binding sugar epimerase/dehydrogenases (Pissowotzki et al., Mol. Gen. Genet. 231: 113-213, 1991). Immediately upstream from ORF6, a nod box-related sequence is present, the arrangement of which is fully consistent with a recently presented model for the nod box structure (Goethals et al., Proc. Natl. Acad. Sci. USA 89: 1646-1650, 1992). Insertional inactivation of ORF6 did not affect the nodulation and fixation performance on S. rostrata. However, on S. formosa roots the nodulation kinetics of such a mutant was clearly affected (about 5 days delay). We propose to call this new symbiotic gene nolK.
Mol Plant Microbe Interact
PMID:Identification of a new inducible nodulation gene in Azorhizobium caulinodans. 147 18

(ADP-ribosyl)ation of chromosomal proteins was studied by incubating the nuclei of brain and liver of young and old rats with 14C-NAD+. In brain as well as in liver histone proteins show approximately 2-3 fold higher (ADP-ribosyl)ation than that of non-histone chromosomal (NHC) proteins of both the age groups. H1 seems to be the major target for (ADP-ribosyl)ation. Amongst nucleosomal histones H2B is the main acceptor of 14C-labelled ADP-ribose moieties. A sharp age related decline of (ADP-ribosyl)ation of chromosomal proteins was observed in both the tissues.
Cell Mol Biol 1992 Jul
PMID:(ADP-ribosyl)ation pattern of chromosomal proteins during ageing. 149 45


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