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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cells exposed to hyperosmotic conditions maintain their volume by accumulating organic osmolytes. Taurine is considered as an osmolyte in brain cells. Accumulation of other osmolytes (sorbitol, myo-inositol and betaine), was shown in renal cells to result from an upregulation of the expression of the genes regulating osmolyte cell content. We have investigated the gene expression of the taurine transporter (TauT) and of the taurine biosynthetic enzymes, cysteine dioxygenase (CDO) and cysteine sulfinate decarboxylase (CSD) by measuring their mRNA levels in brain of salt-loaded rats. mRNA levels of genes previously identified as osmosensitive, namely aldose reductase (AR), myo-inositol transporter (SMIT) and betaine transporter (BGT1) were also determined. In whole brain, TauT-, SMIT- and BGT1-mRNA levels were significantly increased following acute salt-loading but SMIT-mRNA levels only remained elevated following chronic salt-loading while CDO-, CSD- and AR-mRNA levels remained unchanged in both conditions. Following acute salt-loading, mRNA levels of TauT, CDO, CSD, SMIT, BGT1 and AR were increased in cerebral cortex while SMIT- and BGT1-mRNA levels only were increased in striatum and habenula.TauT, CDO and CSD genes may be upregulated in brain of salt-loaded rats but the upregulation of the TauT gene appears more widespread. TauT, CDO and CSD are thus putative osmosensitive genes. However the actual pattern (amplitude, time course and regional occurrence) of the upregulation of each of the putative (TauT, CDO and CSD) and established (AR, SMIT and BGT1) osmosensitive genes differs markedly. This indicates that there exist other factors in brain cells which can selectively prevent the upregulation of these genes by hyperosmolarity.
Brain Res Mol Brain Res 2000 Apr 14
PMID:Gene expression of taurine transporter and taurine biosynthetic enzymes in brain of rats with acute or chronic hyperosmotic plasma. A comparative study with gene expression of myo-inositol transporter, betaine transporter and sorbitol biosynthetic enzyme. 1081 27

A Lactococcus lactis glycine-betaine transport system was identified by functional complementation of an Escherichia coli proP proU mutant with a gene library from L. lactis sbsp. cremoris. The cloned locus forms an operon highly homologous to opuA, encoding a glycine-betaine uptake system of Bacillus subtilis. Disruption of opuA in L. lactis abolished protection by glycine-betaine against elevated osmolarity. OpuA belongs to the so-called "ABC transporters" family, which comprise an extracellularly localized substrate-binding protein. In B. subtilis OpuA system, this binding protein is a lipoprotein, attached to the external face of the cytoplasmic membrane by its lipidic moiety. In contrast, in the L. lactis opuA operon, and in other gram-positive homologues as well, a fusion between the gene encoding the integral membrane protein and the substrate-binding protein components gave rise to a hybrid protein presumably attaching the substrate-binding protein to the surface of the cell via its covalent link to the integral membrane component. Mapping of L. lactis opuA transcription start identified one mRNA, more abundant in cells grown at elevated osmolarity. Construction of an opuA-gusA fusion confirmed that opuA transcription is directed by a promoter osmotically inducible in L. lactis. When recombined upstream from a lac transcriptional fusion in the chromosome of E. coli, the opuA promoter appeared as very strong, and only poorly stimulated by elevated osmotic pressure, suggesting the existence of a specific machinery involved in the osmotic signal transduction in L. lactis.
J Mol Microbiol Biotechnol 2000 Apr
PMID:Characterization of OpuA, a glycine-betaine uptake system of Lactococcus lactis. 1093 45

Elevated homocysteine levels have been associated with arteriosclerosis and thrombosis. Hyperhomocysteinemia is caused by altered functioning of enzymes of its metabolism due to either inherited or acquired factors. Betaine-homocysteine methyltransferase (BHMT) serves, next to methionine synthase, as a facilitator of methyl group donation for remethylation of homocysteine into methionine, and reduced functioning of BHMT could theoretically result in elevated homocysteine levels. Recently, the genomic sequence of the BHMT gene was published. Mutation analysis may reveal mutations of the BHMT gene that could lead to hyperhomocysteinemia. In the present study we performed genomic sequencing of the BHMT gene of 16 vascular patients with hyperhomocysteinemia and detected three mutations in the coding region of this gene. The first was an amino acid substitution of glycine to serine (G199S), which was found only in the heterozygous state. The second mutation was a substitution of glutamine to arginine (Q239R), and the last mutation was an amino acid substitution of glutamine to histidine (Q406H). The latter was also found only in the heterozygous state. The relevance of these mutations was tested in a study group, which consists of 190 cases with vascular disease and 601 controls. The influence of these three mutations on homocysteine levels was investigated. None of the three mutations led to significantly changed homocysteine levels. In addition, no differences in genotype distribution between cases and controls were found. So far, our results provide no evidence for a role of defective BHMT functioning in hyperhomocysteinemia or subsequently in vascular disease.
Mol Genet Metab 2000 Nov
PMID:Betaine-homocysteine methyltransferase (BHMT): genomic sequencing and relevance to hyperhomocysteinemia and vascular disease in humans. 1107 19

The efficiency of betaine absorption into small intestinal slices of broiler chicks was studied in vitro with 14C-labeled betaine. The relative proportion of Na+-coupled betaine uptake, as well as the total uptake capacity was larger in the duodenum than in the jejunum. Dietary betaine increased the Na+-coupled uptake in the duodenum. In in vivo-experiments, methyl-14C-labeled betaine, methionine, or choline was fed to broiler chicks. Betaine appeared in the blood more rapidly, and reached a higher total concentration than choline or methionine. The data suggest that choline and methionine were associated with plasma lipoproteins whereas betaine remained free in the plasma. The label distribution in liver, kidney, and intestinal tissues was studied 24 h after label ingestion. Most of the label from betaine was found in the aquaeous phase in the muscle, while in the liver and jejunum the label from betaine was distributed more evenly between the aquaeous, lipid, and protein phases. Label from choline accumulated in the lipid fraction, particularly so in the liver, whereas label from methionine showed a more variable distribution pattern. The distribution results are interpreted in terms of specific roles of betaine, choline, and methionine in methyl group metabolism.
Comp Biochem Physiol A Mol Integr Physiol 2001 Feb
PMID:Intestinal uptake of betaine in vitro and the distribution of methyl groups from betaine, choline, and methionine in the body of broiler chicks. 1122 88

Glycinebetaine is an important osmoprotectant in bacteria, plants, and animals, but only little information is available on the synthesis of glycinebetaine in tree plants. Among four mangrove species, glycinebetaine could be detected only in Avicennia marina. Pinitol was the main osmoprotectant in the other three species. The level of glycinebetaine in A. marina increased under high salinity. Betaine-aldehyde dehydrogenase (BADH) was detected in all four species, but choline monooxygenase could not be detected. A cDNA library was constructed from the leaves of A. marina. Two kinds of BADH cDNAs were isolated, one homologous to the spinach chloroplast BADH, and the other with unique residues SKL at the end of C-terminus. The BADH transcription levels of the former were higher than those of the latter. The levels of the former BADH increased at high salinity whereas those of the latter were independent of salinity. BADHs were expressed in Escherichia coli and purified. Two kinds of A. marina BADHs exhibited similar kinetic and stability properties, but were significantly different from those of spinach BADH. A. marina BADHs efficiently catalyzed the oxidation of betainealdehyde, but not the oxidation of omega-aminoaldehydes and were more stable at high temperature than the spinach BADH.
Plant Mol Biol 2001 Feb
PMID:Molecular cloning and functional characterization of two kinds of betaine-aldehyde dehydrogenase in betaine-accumulating mangrove Avicennia marina (Forsk.) Vierh. 1129 80

In Experiment 1, the water holding capacity of broiler chick intestinal tissue was studied in vitro. The chicks were fed with corn-based diets with or without a 0.2% betaine supplementation in the drinking water. Slices from duodenum and jejunum were incubated in iso-osmotic (300 mM) or hyperosmotic saline (600 mM) with or without 10 mM betaine. The water volume of tissue slices was studied by adding tritiated water in the incubation medium while [14C]inulin was used to correct for the adherent water. After 30 min of incubation, by which time the steady-state of tritium influx had been achieved, the 3H and 14C-activities of the tissue slices were measured. The ileal and duodenal tissues incubated in the hyperosmotic saline accumulated less tritium than those incubated in iso-osmotic saline. Duodenal slices incubated in hyperosmotic saline with the presence of betaine showed a tritium content similar to slices incubated in iso-osmotic saline. The data suggest that the presence of betaine helped the duodenal, but not jejunal, epithelium to maintain water balance in hyperosmotic conditions. The dietary betaine supplementation diminished the differences between the incubation treatments in duodenal, but not in ileal tissue. In Experiment 2, the same double labeling method, but with shorter incubation times, was used to assess the rate of water flux from the incubation medium to duodenal or jejunal slices. The dietary treatments (as in Experiment 1) had little effect on the results. Betaine in the hyperosmotic saline significantly decreased the rate of tritium accumulation into the tissue slices, indicating that betaine slowed down the influx of water to the epithelium. We suggest that betaine affects the movement of water across the intestinal epithelium and has a role in the osmoregulation of small intestine of broiler chicks.
Comp Biochem Physiol A Mol Integr Physiol 2001 Jun
PMID:Betaine aids in the osmoregulation of duodenal epithelium of broiler chicks, and affects the movement of water across the small intestinal epithelium in vitro. 1142 29

The preferential solvation (PS) in mixed binary solvents, e.g. dichloromethane/acetonitrile, dichloromethane/methanol, acetonitrile/water has been studied by monitoring the charge transfer band of some betaine dyes. Since PS accounts for dielectric as well as specific interactions while dielectric enrichment only for the former, it was shown that in the case of dichloromethane/methanol, hydrogen bonding precedes dielectric enrichment whereas in the case of acetonitrile/water the inverse is true.
Spectrochim Acta A Mol Biomol Spectrosc 2001 Aug
PMID:Study of the preferential solvation of some betaine dyes in binary solvent mixtures. 1150 40

Erwinia chrysanthemi insertion mutants were isolated that grew poorly specifically in the presence of glycine betaine (GB) or its analogues in high-salt media. Transposon insertions were found to affect the bspA gene, which forms an operon including the psd locus coding for phosphatidylserine decarboxylase. Initial GB uptake is not affected by the bspA mutation. However, in high-salt medium, its initial accumulation is followed by a reduced glucose uptake and a release of GB but not a loss of viability. BspA is homologous to the widespread MscS channel, YggB, but does not seem to constitute a mechanosensitive channel. We suggest that BspA is a protein sensing both intracellular GB and the extracellular salt content of the medium, the hypothesis being built on the observation that BspA is necessary to maintain the GB pool during osmoadaptation in high-salt media containing this osmoprotectant.
Mol Microbiol 2001 Oct
PMID:Glycine betaine loses its osmoprotective activity in a bspA strain of Erwinia chrysanthemi. 1167 69

The aim of this experiment was to study the patterns of betaine accumulation into intestinal tissue, liver and plasma of broiler chicks with or without coccidial infection. The chicks were raised on a corn-based, low-betaine diet with or without 1000 ppm betaine supplementation and with or without intestinal microparasite (Eimeria maxima) challenge to the age of 21 days. Plasma, liver, intestinal tissue and digesta of non-challenged (NC) birds and plasma and intestinal tissue of coccidiosis challenged (CC) birds were analysed for betaine content. NC birds were also analyzed for homocysteine in plasma and S-adenosylmethionine (S-AM) in liver. The jejunal epithelium was histologically examined for the presence of coccidia and the crypt-villus ratio was measured. Dietary betaine supplementation decreased the plasma homocysteine concentration but had no effect on liver S-AM of NC birds. The data suggest that chicks on a low-betaine diet accumulate betaine into the intestinal tissue. When the diet was supplemented with betaine, betaine accumulated heavily into liver and to a lesser degree into intestinal tissue. The concentration of betaine in jejunal and ileal digesta was low suggesting that dietary betaine was mainly absorbed from the proximal small intestine. The coccidial challenge decreased the concentration of betaine in the liver, but greatly increased that in the intestinal tissue. The crypt-villus ratio was decreased by the dietary betaine supplementation in healthy and challenged chicks, suggesting that dietary betaine both protects the jejunal villi against coccidial infection and also stabilizes the mucosal structure in healthy broiler chicks. These results support our earlier findings suggesting that betaine is likely to act as an important intestinal osmolyte in broiler chicks.
Comp Biochem Physiol A Mol Integr Physiol 2001 Nov
PMID:Dietary betaine accumulates in the liver and intestinal tissue and stabilizes the intestinal epithelial structure in healthy and coccidia-infected broiler chicks. 1169 12

Exogenously provided proline has been shown to serve as an osmoprotectant in Bacillus subtilis. Uptake of proline is under osmotic control and functions independently of the known transport systems for the osmoprotectant glycine betaine. We cloned the structural gene (opuE) for this proline transport system and constructed a chromosomal opuE mutant by marker replacement. The resulting B. subtilis strain was entirely deficient in osmoregulated proline transport activity and was no longer protected by exogenously provided proline, attesting to the central importance of OpuE for proline uptake in high-osmolarity environments. The transport characteristics and growth properties of the opuE mutant revealed the presence of a second proline transport activity in B. subtilis. DNA sequence analysis of the opuE region showed that the OpuE transporter (492 residues) consists of a single integral membrane protein. Database searches indicated that OpuE is a member of the sodium/solute symporter family, comprising proteins from both prokaryotes and eukaryotes that obligatorily couple substrate uptake to Na+ symport. The highest similarity was detected to the PutP proline permeases, which are used in Escherichia coli, Salmonella typhimurium and Staphylococcus aureus for the acquisition of proline as a carbon and nitrogen source, but not for osmoprotective purposes. An elevation of the osmolarity of the growth medium by either ionic or non-ionic osmolytes resulted in a strong increase in the OpuE-mediated proline uptake. This osmoregulated proline transport activity was entirely dependent on de novo protein synthesis, suggesting a transcriptional control mechanism. Primer extension analysis revealed the presence of two osmoregulated and tightly spaced opuE promoters. The activity of one of these promoters was dependent on sigma A and the second promoter was controlled by the general stress transcription factor sigma B.
Mol Microbiol 1997 Jul
PMID:Osmostress response in Bacillus subtilis: characterization of a proline uptake system (OpuE) regulated by high osmolarity and the alternative transcription factor sigma B. 1190 19


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