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)

Hydroxylamine-induced mutations in the virA gene of Agrobacterium tumefaciens that do not require the plant phenolic-inducing compound acetosyringone for vir regulon induction were isolated. The isolation was based on the activation of both virB::lacZ and virE::cat fusions by mutant virA loci in the absence of acetosyringone. Three of these virA(Ais) (acetosyringone-independent signaling) mutants were characterized. All three mutants expressed a virB::lacZ fusion at high levels in the absence of acetosyringone. One virA (Ais) mutant, virA112, exhibited vir gene expression in the absence of inducing monosaccharides and acidic growth conditions, both of which are normally required for vir gene induction. The phenotype of the virA112 mutant resulted from a glycine to glutamic acid change near His-474, the site of VirA autophosphorylation.
Mol Plant Microbe Interact
PMID:Mutants of the Agrobacterium tumefaciens virA gene exhibiting acetosyringone-independent expression of the vir regulon. 179

Purified C3 binds covalently to Jurkat T cells upon incubation at neutral pH. This binding does not appear to involve proteolysis of C3; it leads to high-molecular-weight associations, preferentially through ester linkages, which are disrupted upon incubation with hydroxylamine at alkaline pH. Part of the association also appears to involve disulfide links between C3 and Jurkat cells. Similarly, plasma membranes purified from these cells bind C3 with no evidence for proteolysis of C3. Binding of C3 appears to be "catalysed" by Jurkat cells, and is not due to the well-known spontaneous hydrolysis of C3. Binding of C3 involves hydrolysis of its thioester bond, as titratable--SH groups are available in soluble C3 after incubation of purified C3 with Jurkat plasma membranes; loss of C3 haemolytic activity confirms this finding. These observations give evidence for the binding of C3b-like C3 to Jurkat cells, conferring on these cells the potential to interact with other complement receptor-bearing cells such as B cells.
Mol Immunol 1991 Jul
PMID:Covalent binding of non-proteolysed C3 to Jurkat T cells. 183 Mar 64

1. We describe two simple procedures for the rapid identification of certain structural features of glycolipid anchors in acetylcholinesterases (AChEs). 2. Treatment with alkaline hydroxylamine (that cleaves ester-linked acyl chains but not ether-linked alkyl chains) converts molecules possessing a diacylglycerol, but not those with an alkylacylglycerol, into hydrophilic derivatives. AChEs in human and bovine erythrocytes possess an alkylacylglycerol (Roberts et al., J. Biol. Chem. 263:18766-18775, 1988; Biochem. Biophys. Res. Commun. 150:271-277, 1988) and are not converted to hydrophilic dimers by alkaline hydroxylamine. Amphiphilic dimers of AChE from Drosophila, from mouse erythrocytes, and from the human erythroleukaemia cell line K562 also resist the treatment with hydroxylamine and likely possess a terminal alkylacylglycerol. This indicates that the cellular pool of free glycolipids used as precursors of protein anchors is distinct from the pool of membrane phosphatidylinositols (which contain diacylglycerols). 3. Pretreatment with alkaline hydroxylamine is required to render the amphiphilic AChE from human erythrocytes susceptible to digestion by Bacillus thuringiensis phosphatidylinositol-specific phospholipase C (PI-PLC) (Toutant et al., Eur. J. Biochem. 180:503-508, 1989). We show here that this is also the case for the AChE from mouse erythrocytes, which therefore likely possesses an additional acyl chain in the anchor that prevents the action of PI-PLC. 4. In two sublines of K562 cells (48 and 243), we observed that AChE either was directly susceptible to PI-PLC (243) or required a prior deacylation by alkaline hydroxylamine (48). This suggests that glycolipid anchors in AChE of K562-48 cells, but not those in AChE of K562-243 cells, contain the additional acylation demonstrated in AChE from human erythrocytes. These observations illustrate the cell specificity (and the lack of species-specificity) of the structure of glycolipid anchors.
Cell Mol Neurobiol 1991 Feb
PMID:Rapid analysis of glycolipid anchors in amphiphilic dimers of acetylcholinesterases. 184 55

Temperature-sensitive mutants defective in 60S ribosomal subunit protein L16 of Saccharomyces cerevisiae were isolated through hydroxylamine mutagenesis of the RPL16B gene and plasmid shuffling. Two heat-sensitive and two cold-sensitive isolates were characterized. The growth of the four mutants is inhibited at their restrictive temperatures. However, many of the cells remain viable if returned to their permissive temperatures. All of the mutants are deficient in 60S ribosomal subunits and therefore accumulate translational preinitiation complexes. Three of the mutants exhibit a shortage of mature 25S rRNA, and one accumulates rRNA precursors. The accumulation of rRNA precursors suggests that ribosome assembly may be slowed in this mutant. These phenotypes lead us to propose that mutants containing the rpl16b alleles are defective for 60S subunit assembly rather than function. In the mutant carrying the rpl16b-1 allele, ribosomes initiate translation at the noncanonical codon AUA, at least on the rpl16b-1 mRNA, bringing to light a possible connection between the rate and the fidelity of translation initiation.
Mol Cell Biol 1991 Nov
PMID:Assembly of 60S ribosomal subunits is perturbed in temperature-sensitive yeast mutants defective in ribosomal protein L16. 192 70

The possibility of tyrosine involvement in steroid binding by rat uterus estrogen receptor (rER) was investigated. Chemical modification of rER with reagents such as tetranitromethane (TNM) and N-acetylimidazole (NAcI) inhibited estradiol binding. Steroid binding was inhibited to a greater extent at pH 8 than at pH 6, indicating the participation of tyrosine (TNM has increasing affinity for cysteine ove tyrosine at pH 6). Inhibition patterns remained similar for incubations at 0-4 degrees C or 37 degrees C. NAcI inhibited rER steroid binding at 37 degrees C, but not at 0-4 degrees C. Hydroxylamine incubated in the presence of rER and NAcI appeared to reverse this inhibition. Thus, these findings indicate that the phenyl ring and possibly the phenolic hydroxyl of tyrosine are involved in steroid binding of the receptor.
J Steroid Biochem Mol Biol 1991 Feb
PMID:Evidence for involvement of tyrosine in estradiol binding by rat uterus estrogen receptor. 200 36

Methyl 3,4-diphenyl-5-hydroxylamino-2-furoate (N-OH-MDPF) (I), methyl 3,4-diphenyl-5-acetoxyamino-2-furoate (N-OAc-MDPF) (II), methyl 3,4-diphenyl-N-hydroxy-5-acetylamino-2-furoate (N-OH-MDPAF) (III), and methyl 3,4-diphenyl-N-acetoxy-5-acetylamino-2-furoate (N-OAc-MDPAF) (IV) were synthesized and tested for mutagenic activity for Salmonella typhimurium TA98 and TA100. The hydroxylamine (I) and acetyl derivatives (II-IV) did not show mutagenic activity in TA98 or TA100. In contrast, the parent nitro compound, methyl 3,4-diphenyl-5-nitro-2-furoate (MDPNF) (V) was found to be equally active in TA98 and TA98-DNP, and more active in TA100 and TA104. The mutagenic activity in TA100 and TA104 decreased significantly under anaerobic conditions. Additionally, MDPNF was previously shown to be less mutagenic in the nitroreductase-deficient derivatives TA100NR and TA98NR, suggesting a requirement for nitro reduction. Incubation of V with NADPH and bacterial lysates of TA98 or TA98NR yielded a metabolite which was identified as I based on chromatographic and mass spectral characteristics. The rate of reduction by the lysate of TA98NR was about one-third that of TA98, showing a correlation between mutagenicity and nitroreductase activity. The lysates of TA98 did not reduce N-OH-MDPF further to the amine. In contrast to the lack of mutagenic activity of I-IV, N-hydroxy-4-aminobiphenyl (N-OH-ABP) and its acetyl derivatives were active in TA98, but less so in TA98-DNP. These data suggest that mechanisms involving O-acetylation of N-hydroxylamine to the acetoxyamine or acyl transfer reactions are not involved in the generation of mutagen from MDPNF. Furthermore, the differential mutagenic response of V in TA98 and TA98NR, its reduction to I, and the lack of activity of I suggest that the intermediates of reduction between the nitro and hydroxylamine, such as nitro or nitroso free radical anions, may be involved in mutagenesis. The decreased response of V under anaerobic conditions and increased response in TA104 suggest that secondary oxygen radicals generated from reduction intermediates may be responsible for the mutagenicity of MDPNF.
Environ Mol Mutagen 1991
PMID:Mutagenicity of N- and O-acetyl derivatives of methyl 3,4-diphenyl-5-hydroxylamino-2-furoate and N-hydroxy-4-aminobiphenyl in Salmonella typhimurium. 200 70

Fatty acid activation, transfer, and reduction by the fatty acid reductase multienzyme complex from Photobacterium phosphoreum to generate fatty aldehydes for the luminescence reaction is regulated by the interaction of the synthetase and reductase subunits of this complex. Identification of the specific site involved in covalent transfer of the fatty acyl group between the sites of activation and reduction on the synthetase and reductase subunits, respectively, is a critical step in understanding how subunit interactions modulate the flow of fatty acyl groups through the fatty acid reductase complex. To accomplish this goal, the nucleotide sequence of the luxE gene coding for the acyl-protein synthetase subunit (373 amino acid residues) was determined and the conserved cysteinyl residues implicated in fatty acyl transfer identified. Using site-specific mutagenesis, each of the five conserved cysteine residues was converted to a serine residue, the mutated synthetases expressed in Escherichia coli, and the properties of the mutant proteins examined. On complementation of four of the mutants with the reductase subunit, the synthetase subunit was acylated and the acyl group could be reversibly transferred between the reductase and synthetase subunits, and fatty acid reductase activity was fully regenerated. As well, sensitivity of the acylated synthetases to hydroxylamine cleavage (under denaturation conditions to remove any conformational effects on reactivity) was retained, showing that a cysteine and not a serine residue was still acylated. However, substitution of a cysteine residue only ten amino acid residues from the carboxyl terminal (C364S) prevented acylation of the synthetase and regeneration of fatty acid reductase activity. Moreover, this mutant protein preserved its ability to activate fatty acid to fatty acyl-AMP but could not accept the acyl group from the reductase subunit, demonstrating that the C364S synthetase had retained its conformation and specifically lost the fatty acylation site. These results provide evidence that the flow of fatty acyl groups in the fatty acid reductase complex is modulated by interaction of the reductase subunit with a cysteine residue very close to the carboxyl terminal of the synthetase, which in turn acts as a flexible arm to transfer acyl groups between the sites of activation and reduction.
J Mol Biol 1991 May 05
PMID:Identification of the acyl transfer site of fatty acyl-protein synthetase from bioluminescent bacteria. 202 62

The hydroxylamine and nitroso metabolites formed by N4-oxidation of sulfonamides are thought to be involved in the pathogenesis of idiosyncratic reactions to this class of drugs. Idiosyncratic reactions to sulfonamides are characterized by multisystemic toxicity, including hepatitis, nephritis, dermatitis, and blood dyscrasias (aplastic anemia, agranulocytosis). We have previously shown that cytochrome P-450 in the liver metabolizes sulfamethoxazole to its hydroxylamine metabolite. In this paper we report the N4-oxidation of sulfamethoxazole by activated monocytes and neutrophils (human and canine) to form sulfamethoxazole hydroxylamine and nitrosulfamethoxazole. The presumed nitroso intermediate was not detected. Purified myeloperoxidase and prostaglandin H synthase were also capable of mediating the oxidation of sulfamethoxazole. The present studies suggest that myeloperoxidase is responsible for the observed oxidation by phagocytic cells. Oxidation by neutrophils may play a role in agranulocytosis, and oxidation by monocytes may facilitate antigen presentation. Extrahepatic bioactivation of sulfonamides by peroxidases in phagocytic cells and other tissues may be important in determining the range of adverse reactions to sulfonamides that occur.
Mol Pharmacol 1990 Nov
PMID:Peroxidase-dependent oxidation of sulfonamides by monocytes and neutrophils from humans and dogs. 217 79

The roles of Ca2+ and cyclic nucleotides as secondary, intracellular messengers for exflagellation of Plasmodium berghei and Plasmodium falciparum were investigated. Treatment with Ca2+ antagonists such as TMB-8 (an inhibitor of intracellular Ca2+ release) or W-7 (a calmodulin inhibitor) strongly inhibited exflagellation induced by alkaline medium at pH 8.0 whereas EGTA (a Ca2+ chelator) or nicardipine and nifedipine (Ca2+ channel inhibitors) had no effect. These results may indicate that mobilization of parasites' internal resources of Ca2+ is a prerequisite for exflagellation. Agents which increase cAMP levels did not induce exflagellation at the non-permissive pH of 7.3, and had no significant inhibitory effect at the permissive pH of 8.0. IBMX (cAMP/cGMP-phosphodiesterase inhibitor), however, enhanced exflagellation at pH 7.3, indicating the possibility that cGMP, but not cAMP, may be involved in the induction of exflagellation. Furthermore, cGMP or agents which increase cGMP levels such as nitroprusside (a potent activator of guanylate cyclase), enhanced exflagellation at pH 7.3, whereas N-methyl-hydroxylamine (guanylate cyclase inhibitor) inhibited the exflagellation at pH 8.0. From these results, it may be concluded that the induction of exflagellation requires both Ca2+ mobilization and an increase in cGMP levels.
Mol Biochem Parasitol 1990 Aug
PMID:Possible roles of Ca2+ and cGMP as mediators of the exflagellation of Plasmodium berghei and Plasmodium falciparum. 217 16

The benzoylarginine peptidase of Treponema denticola (strain ASLM; a human oral spirochaete) was progressively and irreversibly inactivated by 1-(ethoxycarbonyl)-2-ethoxy-1, 2-dihydroquinoline, a carboxyl-group reagent. At acidic pH values, reaction of one mole of the modifier per active site of the enzyme resulted in total inactivation of the enzyme. Assuming that this modifier is a specific carboxyl reagent, the data suggest that the inactivation of the T. denticola benzoylarginine peptidase was caused by the modification of one carboxyl group located close to the active site of the enzyme. Results obtained with Woodward's reagent K (N-ethyl-5-phenylisoxazolium 3'-sulphonate) supported these findings. Carbethoxylation with diethylpyrocarbonate effectively inactivated the enzyme, and addition of hydroxylamine at pH 7.0 restored the activity almost totally, suggesting that the pyrocarbonate had reacted with tyrosyl or histidyl residues.
Mol Microbiol 1990 Aug
PMID:The benzoylarginine peptidase from Treponema denticola (strain ASLM), a human oral spirochaete: evidence for active-site carboxyl groups. 228 Jun 91


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