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)

Replication-deficient mutants of the unit-copy miniplasmid lambda-P1:5R were isolated after hydroxylamine mutagenesis. Complementation tests showed that the majority of these mutants are defective in the production of the repA protein product. Two of these mutants have suppressible nonsense (amber) mutations. The DNA sequence of one of these, repA103, has been determined. The lesion lies within the repA open reading frame, showing that the repA product is essential for plasmid replication. Complementation of deletion mutants of lambda-P1:5R by repA protein showed that the origin of replication lies to the left of repA and that this 300-base-pair origin region is the only portion of the DNA essential for plasmid replication if repA protein is supplied in trans. Six of the 21 hydroxylamine-induced mutants were not complemented by repA. Replication of three of these could be restored by introduction into the plasmid of a wild-type origin region, suggesting that they were origin-defective. The DNA sequence of two mutants was determined. Mutant rep-11 has a 43-base-pair deletion within the incC sequence (incC is a series of five direct repeats of a 19-base-pair sequence known to be involved in the regulation of plasmid replication). The deletion appears to have been generated by homologous recombination between two repeats. Mutant rep-30 has a single base substitution in a region just to the left of incC that destroys one of five G-A-T-C (dam methylation) sites in this region. As lambda-P1:5R is unable to establish itself as a plasmid in a methylase-defective (dam-) strain, it seems probable that methylation of the G-A-T-C sequences is important for origin function. The incC region and the sequences to its left appear to constitute an essential part of the origin of replication.
J Mol Biol 1985 May 25
PMID:Trans- and cis-acting elements for the replication of P1 miniplasmids. 400 24

The rat hepatic microsomal oxidation of amine metabolites of mono-and dinitrotoluene isomers has been investigated. Microsomes catalyzed the NADPH-dependent oxidation of 2-amino-6-nitrobenzyl alcohol, 2-amino-4-nitrobenzyl alcohol, and the isomeric aminobenzyl alcohols to ethyl acetate-extractable compounds capable of reducing ferric iron. The microsomal metabolism of 2-amino-6-nitrobenzyl alcohol, a metabolite of the hepatocarcinogen 2,6-dinitrotoluene, was characterized in detail. High pressure liquid chromatographic analysis indicated the formation of two metabolites, both of which were reducing agents. One metabolite was identified as 2-hydroxylamino-6-nitrobenzyl alcohol by comparison of its chromatographic properties and mass spectrum with those of the authentic compound. Mass spectral, proton NMR, and UV-visible spectroscopic studies suggested that the other metabolite was 2-amino-5-hydroxy-6-nitrobenzyl alcohol. The microsomal oxidation of 2-aminobenzyl alcohol also resulted in the formation of two reducing agents, one of which was the corresponding hydroxylamine. The formation of 2-hydroxylamino-6-nitrobenzyl alcohol from the microsomal oxidation of 2-amino-6-nitrobenzyl alcohol was linear with respect to time for at least 20 min, while aminophenol formation was only linear for 3 min. The rate of the microsomal oxidation of 2-amino-6-nitrobenzyl alcohol was decreased by known inhibitors of cytochrome P-450, while heat inactivation of microsomal flavin-containing monooxygenase had no effect. The rate of formation of both metabolites was increased 1.5-fold by phenobarbital pretreatment. Pretreatment with beta-naphthoflavone had no effect on the rate of N-hydroxylation, while a small but statistically significant increase in the rate of C-hydroxylation (117% of control) was observed. The rate of oxidation of 2-amino-6-nitrobenzyl alcohol was lower with microsomes from female rats than with those from males, yielding male/female ratios of 1.34 for aminophenol formation and 3.26 for hydroxylamine formation. These data indicate that 2-amino-6-nitrobenzyl alcohol, a metabolite of the hepatocarcinogen 2,6-dinitrotoluene, can be N-hydroxylated by hepatic microsomal cytochrome P-450. The results are consistent with the hypothesis that a hydroxylamine metabolite of 2,6-dinitrotoluene is sulfated in vivo to produce an electrophilic species.
Mol Pharmacol 1985 Aug
PMID:Characterization of the oxidation of amine metabolites of nitrotoluenes by rat hepatic microsomes. N- and C-hydroxylation. 402 2

It was shown that eosine and erythrosine are competing inhibitors of the Ca2+-Mg2+- dependent ATPase active center of sarcoplasmic reticulum. The eosine and erythrosine inhibition constants are equal to 1.4 x 10(-6) M and 1.1 x 10(-6) M, respectively. Nitroxide radicals of various hydrophobicity and K3Fe(CN)6 were used to compare the constants of triplet states exchange quenching of erythrosine in aqueous solution, in lecithine liposomes and in ATPase active center of sarcoplasmic reticulum. It was established that ATPase binding center was immersed into a liquid phase and was not connected with lipids. Mn2+ and Gd3+-ions, which are competing with Mg2+ and Ca2+ for binding sites in the enzyme active center, diminished the phosphorescence quenching time of eosine at 77K. This means that the ion binding sites are less than 12 A apart from ATP-binding center.
Mol Biol (Mosk)
PMID:[Study of catalytically active center of the Ca2+-Mg2+-dependent ATPase of sarcoplasmic reticulum by triplet probe method]. 613 Apr 71

Beta-2 microglobulin (beta 2M) is a 12,000 dalton protein associated with membrane-bound cell surface antigens. Variants of beta 2M, beta 2MA and beta 2MB, were first detected by Michaelson et al. (Immunogenetics 11, 93-95, 1980). An improved method was used to purify beta 2MA and beta 2MB from BALB/c and C57BL/6 mouse livers, respectively. Reproducible yields of 10% were obtained. The purifications were accomplished by a 3 M sodium thiocyanate (NaSCN) extraction of a crude membrane fraction, an acid precipitation step, gel filtration on Sephadex G-75 and ion-exchange chromatography on DEAE-cellulose and CM-cellulose in that order. The elution profile of beta 2MA and beta 2MB on the ion-exchange columns was found to be different, indicating the presence of structural changes. beta 2MA was found to be more acidic (pI = 7.35) than beta 2MB (pI = 7.68) by isoelectric focusing in gels. Complete sequence analysis of beta 2MA and partial sequence analysis of beta 2MB (61 of 99 residues) were performed by automated Edman degradation of the intact chain and of the overlapping peptides obtained by: (a) tryptic cleavage at arginines after acetimidation of lysine side chains, (b) BNPS-skatole cleavage at tryptophan residues and (c) hydroxylamine cleavage at asparagine-glycine linkages. A comparison of the primary structure of beta 2MA to the partial amino acid sequence obtained for beta 2MB revealed a single amino acid substitution (aspartic acid for alanine at position 85) that accounts for the differences in biochemical properties observed.
Mol Immunol 1982 Mar
PMID:Purification and characterization of mouse beta-2 microglobulin: allelic variants from two different strains. 617 66

Guanylyltransferase, an enzyme that catalyzes formation of mRNA 5'-terminal caps, was isolated from HeLa cell nuclei. The partially purified preparation, after incubation with [alpha-32P]GTP, yielded a single radiolabeled polypeptide by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The guanylylated product was stable at neutral and alkaline pHs and had a pI of 4 by isoelectric focusing. An apparent molecular weight of approximately 68,000 was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. The formation of a covalently linked, radiolabeled GMP-protein complex and the associated release of PPi required the presence of [alpha-32P]GTP and divalent cations and incubation between pH 7 and 9. Reaction with [beta-32P]GTP, [alpha-32P]CTP, [alpha-32P]UTP, or [alpha-32P]ATP did not label the approximately 68,000-dalton polypeptide. Phosphoamide linkage of the GMP-enzyme complex was indicated by its sensitivity to cleavage by acidic hydroxylamine or HCl and not by NaOH or alkaline phosphatase. Both formation of the GMP-enzyme intermediate and synthesis of cap structures of type GpppApG from GTP and ppApG were remarkably temperature independent; the rates of enzyme activity at 0 to 4 degrees C were 30% or more of those obtained at 37 degrees C. Radiolabeled GMP-enzyme complex, isolated by heparin-Sepharose chromatography from reaction mixtures, functioned effectively as a GMP donor for cap synthesis with 5'-diphosphorylated oligo- and polynucleotide acceptors. Alternatively, protein-bound GMP could be transferred to PPi to form GTP. The formation of a guanylylated enzyme intermediate appears to be characteristic of viral and cellular guanylyltransferases that modify eucaryotic mRNA 5' termini.
Mol Cell Biol 1982 Aug
PMID:Covalent guanylyl intermediate formed by HeLa cell mRNA capping enzyme. 629 Aug 77

Polypeptides co-purifying with DNA in alkali are covalently bound to DNA. DNA purified by treatment with alkali, sodium dodecyl sulphate and phenol absorbed 125I under conditions designed to radioiodinate exclusively tyrosine and histidine in peptides. A significant amount of the absorbed 125I remained associated with DNA during treatment with phenol as well as during precipitation with ethanol from neutral and alkaline solutions. However, after prolonged digestion with proteinase K, most of the radiolabelled material could be removed from 125I-treated DNA. Further treatment with a second protease (Pronase) released no larger fraction of the 125I label. The residual radiolabelled material could be precipitated together with DNA by ethanol and it remained associated with DNA also in the presence of alkali (95 degrees C), acid (37 degrees C) and hydroxylamine (37 degrees C). In contrast, radiolabelled peptides were released from DNA by treatment with hot piperidine (10% at 95 degrees C) and by agents that hydrolyse peptides and modify DNA, e.g. strong acid (95 degrees C) and formic acid/diphenylamine. The radiolabelled peptides, once released from DNA by these chemical methods, could be further cleaved by Pronase. This shows that the residual DNA/peptide complex isolated after prolonged protease digestion is protease-resistant unless it is cleaved or otherwise modified by harsh chemical treatment. The linking groups between deoxynucleotides and the radiolabelled residual peptides could be isolated by digestion of DNA in the DNA/peptide complex. Radiolabelled peptides could be released from this linking group material by phosphodiesterases, indicating the involvement of phosphodiesters in the linking groups.
J Mol Biol 1983 Feb 25
PMID:Phosphodiester bonds between polypeptides and chromosomal DNA. 630 72

We have previously demonstrated that the sequence 5'TGGCAA 3' located at codons 32-33 of the rIIB gene of bacteriophage T4 is a hotspot for transition mutations (Nelson et al. 1981). Here I report the properties of the same TGGCAA sequence introduced into the gene at codons 11-12. The sequence is highly mutable in both locations, suggesting that its high mutability is due to features of the TGGCAA itself and is not dependent on the immediate juxtaposition of additional external sequences. Within this sequence, at either location, only the transition at the central G:C pair frequently arises spontaneously or by 2-aminopurine or ethylmethane sulfonate mutagenesis. However, the 3' G:C pair, in addition, is highly mutable after nitrous acid or hydroxylamine treatment. This suggests that, within the TGGCAA sequence, there are two hotspots which are targeted by different mutagens.
Mol Gen Genet 1984
PMID:A hotspot for transition mutations in the rIIB gene of bacteriophage T4. I. The extent of the hotspot. 631 44

Seven mutants of Haemophilus influenzae strain Rd (mmsA-) have been isolated that are more sensitive to methyl methane sulfonate (mms) than recombination-deficient (recA-) mutants. The mutations cotransformed about 25% with the strA locus while the five studied clustered tightly; they are all probably allelic. The mutants are not sensitive to ultraviolet radiation, X-rays, or nitrous acid. Mms-damaged phage HP1 plated very inefficiently on these mutants, indicating that they lack the first step in the excision repair of the lesion N3-methyladenine (m3A). Incubation of damaged phage at 30 degrees C in the absence of mms resulted in a steady decline of viability when the phage were plated on the wild mmsA+ host but an initial steep rise was seen when it was plated on an mmsA- mutant. The rise is explained by the assumption that m3A lesions hydrolyzed off the DNA giving rise to repairable apurinic sites by both the mmsA+ and mmsA- hosts. No decline in viability was observed when hydroxylamine was present in the medium. This compound is known to prevent or slow down beta-elimination. The delayed decline in viability is therefore explained by assuming that apurinic sites give rise to beta-elimination-induced single strand breaks in the phage DNA that cannot be repaired by either host. Marker rescue experiments indicated that these breaks did not interrupt injection of phage DNA.
Mol Gen Genet 1983
PMID:Repair of methyl methane sulfonate-damaged phage by Haemophilus influenzae. 660 66

The lethal and mutagenic effects of methyl methanesulphonate (MMS), ethyl methanesulphonate (EMS), and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) can be dissociated in a mitomycin C (MTC)-sensitive mutant, strain 302, of Micrococcus radiodurans. As regards lethality 302 is extremely sensitive, compared with the wild type, to MTC and decarbamoyl MTC (DCMTC), slightly sensitive to EMS, MNNG, nitrous acid, 7-bromomethylbenz[alpha]anthracene (BrMBA), and N-acetoxy-N-2-acetylaminofluorene (AAAF), and resistant to MMS, hydroxylamine, and ICR 191G. As regards mutability it is, compared to the wild type, very sensitive to MMS, EMS, and MNNG, and slightly sensitive to hydroxylamine and nitrous acid but not to any other agent examined. Alkaline sucrose gradient studies indicate the 302 does not incise DNA containing BrMBA adducts, although it does incise DNA damaged by AAAF but probably not to the same extent as wild type. We put forward the hypothesis that the hypermutability of 302 is due to the non-removal of bases or nucleotides, modified in exocyclic positions, which have altered base-pairing capabilities, while lethality results from the non-removal of bases or nucleotides, also modified in exocyclic positions, which no longer form hydrogen-bonded base pairs.
Mol Gen Genet 1980
PMID:Defective excision repair in a mutant of Micrococcus radiodurans hypermutable by some monofunctional alkylating agents. 693 92

Amber mutants of the mini-F plasmid pML31 were isolated with the mutagen hydroxylamine. Under non-permissive conditions amber mutants segregate and show no incorporation of label into supercoiled plasmid DNA in double-label experiments. Wild-type and one mutant of mini-F were integrated by recombinant DNA techniques into the single EcoRI site of plasmid vector pBR322. Plasmid specific proteins were labeled in minicells and analysed by SDS-PAGE. A 34,000 dalton molecular weight protein was identified to be missing in the amber mutant of plasmid mini-F.
Mol Gen Genet 1980
PMID:Amber-mutants of plasmid mini-F defective in replication. 700 8


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