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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Incubation of CMP in 2H2O with 0.5M cysteine methyl ester at p2H 5 and 37 degrees C for 24 h resulted in 43% exchange of 5-H to 5-2H. No deamination of the cytosine nucleus was noted during this treatment. Native and denatured DNA samples from calf thymus were treated in 3H2O with cysteine methyl ester at pH 5 and 37 degrees C for 24 h and incorporation of tritium into each DNA base was determined by enzymic digestion of the treated DNA. The order of the specific radioactivity found was cytosine greater than guanine greater than adenine greater than thymine for denatured DNA and guanine greater than adenine approximately cytosine greater than thymine for native DNA. The ratio of radioactivity for denatured/native was 11.6 for cytosine, 1.5 for guanine, 1.8 for adenine and 1.1 for thymine. Hence the incorporation in cytosine under the reaction conditions is preferential for single-stranded, nonhelical regions of DNA. Escherichia coli glutamic acid tRNA II was treated in 3H2O with 1.24 M cysteine methyl ester at pH 5 and 37 degrees C. The 24-h-treated tRNA was digested with ribonuclease T1 and the fragments were fractionated. Each fragment was then digested with ribonuclease T2 into mononucleotides and the radioactivity distribution among the bases was determined. The average radioactivity found for each of the bases of the four major nucleotides was cytosine greater than guanine approximately adenine greater than uracil. The radioactivity in cytosine varied greatly among the RNase T1 fragments, the ratio of the highest to the lowest radioactivity being 18.7. The corresponding value for guanine was 11.1, for adenine 4.73 and for uracil 3.64. Based on the data obtained, it was deduced that in this tRNA the anticodon loop, the dihydrouridine loop and the extra loop were "exposed" under the conditions employed for the labeling. The 5'-terminal cytosine of the anticodon loop was in a "non-exposed" state, a situation similar to that previously reported for E. coli tyrosine tRNA [Cashmore, A. R., Brown, D. M. & Smith, J. D. (1971) J. Mol. Biol. 59, 359-373] and for E. coli formylmethionine tRNA [Goddard J. P.+Schulman L. H. (1972) J. Biol. Chem. 247, 3864-3867]. Both cytosine 48, located at the 3'-terminal of the extra loop, and guanine 15 in the dihydrouridine loop were in an "emposed" state. This finding does not agree with a tRNA model in which this pair of cytosine and guanine, commonly found in tRNA sequences, forms hydrogen bondings. Positions 30--32, 61--64 and 71, which are located in the stems, were found to be strongly "buried".
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PMID:Conformation of Escherichia coli glutamic acid tRNA II as studied by hydrogen-tritium exchange catalyzed by cysteine methyl ester. 0 69

We have determined the nucleotide sequence of the polC gene of Bacillus subtilis which codes for DNA polymerase III. Our recent analysis has revealed that the gene comprises 4311 nucleotides, from the start to the stop codon, 306 nucleotides more than we reported earlier. The plasmid reported by us and by N.C. Brown's laboratory contained a sequence at the end of the gene which is not related to the polC region of B. subtilis. We have isolated the rest of the gene, the sequence of which is presented in this paper. The new stop codon is followed by a hyphenated palindromic sequence of 13 nucleotides. The C-terminus of the coding region contains the novel mutation, dnaF, which results in a defect in the initiation of replication due to a change in the codon TCC to TTC (serine to phenylalanine). The hypermutator mutation mut-1 is due to two point mutations in the 3' to 5' exonuclease domain, the proof reading function. The codon changes are GGA to GAA (glycine to glutamic acid) and AGC to AAC (serine to asparagine). The elongation defective mutation, polC26, affecting the catalytic site that adds nucleotides to the growing chain, is due to a change in the codon GTC to GAC (valine to aspartic acid). It is separated from the mutation reported earlier, azp-12, by 306 nucleotides. Knowing the locations of the mutational sites allowed us to deduce the domains of the gene and the enzyme it encodes, and permitted us to present a precise map of the gene at the molecular level.
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PMID:Genetic structure and domains of DNA polymerase III of Bacillus subtilis. 184 Jun 38

We reported previously the purification of a 165-kDa muscle-specific protein identified by virtue of its ability to bind 125I-labeled low density lipoprotein with high affinity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Hoffmann, S. L., Brown, M. S., Lee, E., Pathak, R. K., Anderson, R. G. W., and Goldstein, J. J. (1989) J. Biol. Chem. 264, 8260-8270). The protein is located in the lumen of the sarcoplasmic reticulum, where it has no access to plasma lipoproteins. It binds to 45Ca2+ on nitrocellulose blots and stains metachromatically blue with Stains-all, a cationic dye that stains Ca2+-binding proteins. In the current paper, we have isolated a full-length rabbit cDNA clone for the 165-kDa protein. The deduced amino acid sequence reveals a 852-amino acid protein with the following structural features: 1) an NH2-terminal 27-residue putative signal sequence; 2) a highly repetitive region containing nine nearly identical tandem repeats of 29 residues, each consisting of a histidine-rich sequence HRHRGH, a stretch of 10-11 acidic amino acids, and a sequence containing 2 serines and a threonine in a negatively charged context; 3) a 13-residue stretch of polyglutamic acid; and 4) a COOH-terminal cluster of 14 closely spaced cysteine residues with the repeating pattern of Cys-X-X-Cys suggestive of a heavy metal binding domain. Histidine, aspartic acid, and glutamic acid accounted, respectively, for 13, 12, and 19% of the amino acids. The protein does not share any significant sequence homology with the cell surface low density lipoprotein receptor. Stretches of acidic amino acids are a feature of two other luminal sarcoplasmic reticulum proteins, suggesting that these may be a general feature of luminal sarcoplasmic reticulum proteins. We suggest that the histidine-rich Ca2+-binding protein described in the current study be designated HCP. The role of HCP in Ca2+ homeostasis in the sarcoplasmic reticulum of skeletal and cardiac muscle remains to be determined.
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PMID:Molecular cloning of a histidine-rich Ca2+-binding protein of sarcoplasmic reticulum that contains highly conserved repeated elements. 280 65

A number of species respond to bacterial endotoxin (lipopolysaccharide [LPS]) wherein cells of the monocyte-macrophage lineage are rapidly induced either directly or via T-cell collaboration to initiate the extrinsic coagulation protease pathway. This results in fibrin formation and deposition as well as consumption of plasma coagulation proteins. It has been claimed that this cellular response, basic to the Shwartzman reaction, is lacking in rats and may account for the more limited severity of the Shwartzman reaction in this species. We examined the in vitro lymphoid procoagulant response in Fischer 344, Brown Norway, and Lewis rats. When peripheral blood mononuclear cells (PBM) were stimulated in vitro with LPS, a procoagulant activity (PCA) response was observed when assayed by acceleration of clotting of recalcified human or rat platelet-poor plasma. The response was rapid, with a maximum achieved at 4 h. PCA was not physically dissociated from viable PBM by 5 mM EDTA, which is consistent with the presence of an intrinsic plasma membrane initiator molecule rather than calcium-bound gamma-carboxylated glutamic acid-containing proteases. The induction of monocyte PCA was prevented by incubation of cells with cycloheximide or actinomycin D, implicating a new biosynthetic requirement. Cultivation of PBM with warfarin did not diminish the function of the effector PCA, nor did vitamin K augment the function of the endotoxin-induced PCA, indicating that the functional activity was not attributable to gamma-carboxylated glutamic acid-containing proteins. No inhibition of the cellular PCA molecule was produced by serine protease inhibitors. The LPS-induced PCA appeared to involve a tissue factor-like molecule since both factors X and VII were required in mediating PCA. Isolation of monocytes and T lymphocytes from LPS-stimulated PBM demonstrated that PCA was present in the monocyte-rich fraction. When isolated rat T lymphocytes and monocytes were separately exposed to LPS, PCA was not induced. In contrast, when the cells were combined, LPS induced PCA, indicating that the PCA response involved cellular collaboration between cells present in T lymphocyte and monocyte populations.
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PMID:Lymphoid procoagulant response to bacterial endotoxin in the rat. 384 Jul 72

The process of functional adaptation after extensive small bowel resection is complex and imprecisely understood. In vivo electrophysiological measurements for monitoring the functional adaptive process after massive small bowel resection in Brown-Norway rats were evaluated. Rats underwent either a sham operation (SH) or a 90% small bowel resection (SB). Standard rat chow was fed in unlimited quantities. At three or 10 weeks after operation, jejunal and ileal transepithelial potential differences (PD, mV) were determined. Electrogenic ion transport in the villus was measured after glucose (sodium coupled active glucose absorption; PD-glu) and in the crypt, after theophylline infusion (theophylline stimulated chloride secretion; PD-theo). Biopsies were taken simultaneously. Each experimental group consisted of three to five animals. At three weeks the PD-theo and PD-glu in SB rats were significantly lower than in SH rats in both jejunal and ileal segments. At 10 weeks PD-theo and PD-glu were significantly diminished in the jejunal segment of the SB rats compared with the SH rats. The values of PD-theo and PD-glu in the ileal segments were, however, no longer different between the two groups. Three and 10 weeks after operation the length of the villi in the SB group was increased significantly compared with the SH controls. These results indicate that in the early phase of adaptation in vivo electrophysiological variables do not correlate with histological changes in the SB rats. This might be due to cell immaturity resulting from an increased rate of cell turnover or lack of intercellular tight junctions. This hypothesis is supported by a recovery of PD responses in the ileum 10 weeks after resection.
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PMID:The value of in vivo electrophysiological measurements for monitoring functional adaptation after massive small bowel resection in the rat. 850 63

The crystal structure of Escherichia coli dihydrofolate reductase (ecDHFR, EC 1.5.1.3) as a binary complex with folinic acid (5-formyl-5,6,7,8-tetrahydrofolate; also called leucovorin or citrovorum factor) has been solved in two space groups, P6(1) and P6(5), with, respectively, two molecules and one molecule per asymmetric unit. The crystal structures have been refined to an R-factor of 14.2% at resolutions of 2.0 and 1.9 A. The P6(1) structure is isomorphous with several previously reported ecDHFR binary complexes [Bolin, J.T., Filman, D.J., Matthews, D.A., Hamlin, R.C., & Kraut, J. (1982) J. Biol. Chem. 257, 13650-13662; Reyes, V.M., Sawaya, M.R., Brown, K.A., & Kraut, J. (1995) Biochemistry 34, 2710-2723]; enzyme and ligand conformations are very similar to the P6(1) 5,10-dideazatetrahydrofolate complex. While the two enzyme subdomains of the P6(1) structure are nearly in the closed conformation, exemplified by the methotrexate P6(1) binary complex, in the P6(5) structure they are in an intermediate conformation, halfway between the closed and the fully open conformation of the apoenzyme [Bystroff, C., Oatley, S.J., & Kraut, J. (1990) Biochemistry 29, 3263-3277]. Thus crystal packing strongly influences this aspect of the enzyme structure. In contrast to the P6(1) structure, in which the Met-20 loop (residues 9-23) is turned away from the substrate binding pocket, in the P6(5) structure the Met-20 loop blocks the pocket and protrudes into the cofactor binding site. In this respect, the P6(5) structure is unique. Additionally, positioning of a Ca2+ ion (a component of the crystallization medium) is different in the two crystal packings: in the P6(1) structure it lies at the boundary between the two molecules of the asymmetric unit, while in P6(5) it coordinates two water molecules, the hydroxyl group of an ethanol molecule, and the backbone carbonyl oxygens of Glu-17, Asn-18, and Met-20. The Ca2+ ion thus stabilizes a single turn of 3(10) helix (residues 16-18 in the Met-20 loop), a second unique feature of the P6(5) crystal structure. The disposition of the N5-formyl group in these structures indicates formation, at least half of the time, of an intramolecular hydrogen bond between the formyl oxygen and O4 of the tetrahydropterin ring. This observation is consistent with the existence of an enol-keto equilibrium in which the enolic tautomer is favored when a hydrogen-bond acceptor is present between O4 and N5. Such would be the case whenever a water molecule occupies that site as part of a hypothetical proton-relay mechanism. Two arginine side chains, Arg-52 in the P6(5) structure and Arg-44 in molecule A of the P6(1) structure, are turned away drastically from the ligand (p-aminobenzoyl)glutamic acid moiety as compared with previously reported DHFR binary complex structures. As in the ecDHFR dideazatetrahydrofolate complex, in both the P6(1) and P6(5) structures a water molecule bridges pteridine O4 and Trp-22(N epsilon 1) with ideal geometry for hydrogen bonding, perhaps contributing to the slow release of 5,6,7,8-tetrahydrofolate from the enzyme-product complex. When either the P6(1) or the P6(5) structures are superimposed with the NADPH holoenzyme [Sawaya, M. R. (1994) Ph.D. Dissertation, University of California, San Diego], we find that the distances between the nicotinamide C4 and pteridine C6 and C7 are very short, 2.1 and 1.7 A in the P6(1) case and 2.0 and 1.4 A in the P6(5) case, perhaps in part explaining the more rapid release of tetrahydrofolate from the enzyme-product complex when NADPH is bound.
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PMID:Crystal structures of Escherichia coli dihydrofolate reductase complexed with 5-formyltetrahydrofolate (folinic acid) in two space groups: evidence for enolization of pteridine O4. 867 26

When the protonated retinal Schiff base dissociates in the photocycle of the proton pump bacteriorhodopsin, asp-85 is the proton acceptor. Replacing this residue with threonine confers halorhodopsin-like properties on the protein, including chloride transport [Sasaki, J., Brown, L.S., Chon, Y.-S., Kandori, H., Maeda, A., Needleman, R., & Lanyi, J.K. (1995) Science 269, 73-75]. However, the electrostatic interaction between the vicinity of residue 85 and glu-204, a residue located about 10 A away near the extracellular surface, that is a part of the proton transport mechanism, should still exist. We find that in the D85T mutant glu-204 becomes protonated when chloride is added. This indicates that the binding of chloride at thr-85 must be equivalent to deprotonation of asp-85. The protonation state of glu-204 reports therefore on the presence or absence of chloride bound at thr-85. During the chloride-transport cycle of D85T, but not D85T/E204Q, fluorescein and pyranine detect the transient release of protons from the protein to the surface and the bulk. The release and the subsequent uptake of the protons occur during the rise and decay of a red-shifted photointermediate, respectively, and confirm the earlier suggestion that this state has the same role in the chloride transport as the M intermediate in the proton transport. Consistent with the red-shift of the absorption maximum, the chloride bound near the Schiff base had already moved away, presumably to be released at the cytoplasmic surface, but another chloride ion has not yet been taken up from the extracellular surface. The switch of the connectivity of the chloride binding site from the cytoplasmic to the extracellular membrane surface must occur therefore during the lifetime of this photointermediate.
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PMID:Interaction of proton and chloride transfer pathways in recombinant bacteriorhodopsin with chloride transport activity: implications for the chloride translocation mechanism. 897 74

In work previously reported (J. A. Gutierrez, P. J. Crowley, D. P. Brown, J. D. Hillman, P. Youngman, and A. S. Bleiweis, J. Bacteriol. 178:4166-4175, 1996), a Tn917 transposon-generated mutant of Streptococcus mutans JH1005 unable to synthesize glutamate anaerobically was isolated and the insertion point of the transposon was determined to be in the icd gene encoding isocitrate dehydrogenase (ICDH). The intact icd gene of S. mutans has now been isolated from an S. mutans genomic plasmid library by complementation of an icd mutation in Escherichia coli host strain EB106. Genetic analysis of the complementing plasmid pJG400 revealed an open reading frame (ORF) of 1,182 nucleotides which encoded an enzyme of 393 amino acids with a predicted molecular mass of 43 kDa. The nucleotide sequence contained regions of high (60 to 72%) homology with icd genes from three other bacterial species. Immediately 5' of the icd gene, we discovered an ORF of 1,119 nucleotides in length, designated citZ, encoding a homolog of known citrate synthase genes from other bacteria. This ORF encoded a predicted protein of 372 amino acids with a molecular mass of 43 kDa. Furthermore, plasmid pJG400 was also able to complement a citrate synthase (gltA) mutation of E. coli W620. The enzyme activities of both ICDH, found to be NAD+ dependent, and citrate synthase were measured in cell extracts of wild-type S. mutans and E. coli mutants harboring plasmid pJG400. The region 5' from the citZ gene also revealed a partial ORF encoding 264 carboxy-terminal amino acids of a putative aconitase gene. The genetic and biochemical evidence indicates that S. mutans possesses the enzymes required to convert acetyl coenzyme A and oxalacetate to alpha-ketoglutarate, which is necessary for the synthesis of glutamic acid. Indeed, S. mutans JH1005 was shown to assimilate ammonia as a sole source of nitrogen in minimal medium devoid of organic nitrogen sources.
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PMID:Role of the citrate pathway in glutamate biosynthesis by Streptococcus mutans. 900 16

Changes in the concentrations of gamma-aminobutyric acid (GABA), soluble calcium ions, glutamic acid, and the activity of glutamate decarboxylase (GAD) were investigated in non-germinated vs. germinated brown rice. Brown rice was germinated for 72 h by applying each of the following solutions: (1) distilled water, (2) 5 mM lactic acid, (3) 50 ppm chitosan in 5 mM lactic acid, (4) 5 mM glutamic acid, and (5) 50 ppm chitosan in 5 mM glutamic acid. GABA concentrations were enhanced in all of the germinated brown rice when compared to the non-germinated brown rice. The GABA concentration was highest in the chitosan/glutamic acid that germinated brown rice at 2,011 nmol/g fresh weight, which was 13 times higher than the GABA concentration in the non-germinated brown rice at 154 nmol/g fresh weight. The concentrations of glutamic acid were significantly decreased in all of the germinated rice, regardless of the germination solution. Soluble calcium and GAD were higher in the germinated brown rice with the chitosan/glutamic acid solution when compared to the rice that was germinated in the other solutions. GAD that was partially purified from germinated brown rice was stimulated about 3.6-fold by the addition of calmodulin in the presence of calcium. These data show that the germination of brown rice in a chitosan/glutamic acid solution can significantly increase GABA synthesis activity and the concentration of GABA.
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PMID:Stimulation of gamma-aminobutyric acid synthesis activity in brown rice by a chitosan/glutamic acid germination solution and calcium/calmodulin. 1278 89

In the present work we investigated the effects of brown rice extracts on proliferation and apoptosis of cancer cells. Brown rice extracts were prepared using nongerminated brown rice versus germinated brown rices. Mouse leukemia L1210 cells, human acute lymphoblastic leukemia Molt4 cells, and human cervical cancer HeLa cells were treated with either nongerminated brown rice extract (N ex), water-germinated extract (W ex), chitosan-germinated extract (C ex), glutamic acid-germinated brown rice extract (G ex), or chitosan/glutamic acid-germinated brown rice extract (CG ex). The concentrations of gamma-aminobutyric acid (GABA) in the G ex and CG ex were three and 3.3 times higher than the GABA concentration in the N ex, respectively. The G ex and CG ex retarded significantly the proliferation rates of L1210 and Molt4 cells, and the highest retardation rate was with CG ex. In addition, the G ex and CG ex enhanced significantly apoptosis of the cultured L1210 cells, but no significant apoptosis was seen with the other extracts, which have lower concentrations of GABA than G ex and CG ex. These results show that brown rice extracts with enhanced levels of GABA have an inhibitory action on leukemia cell proliferation and have a stimulatory action on the cancer cell apoptosis.
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PMID:Effects of germinated brown rice extracts with enhanced levels of GABA on cancer cell proliferation and apoptosis. 1511 48


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