Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rabbit lacrimal gland secretes retinol bound to a 20-21 kDa protein. To test the hypothesis that this protein might be retinol-binding protein (RBP) we probed lacrimal gland for RBP mRNA and lacrimal gland fluid for RBP. A rabbit RBP cDNA clone was used to probe rabbit and rat lacrimal gland RNA using RNase protection analysis. The lacrimal gland contains RBP mRNA at a level 0.1 to 0.03% of that observed in the liver. This RBP mRNA was identical to that observed in the liver based on RNase protection analysis, Northern blot analysis and primer extension analysis. The RBP mRNA levels in the lacrimal gland were not altered by the retinol status of the rabbits. We analysed lacrimal gland fluid for RBP by immunoblotting using a monoclonal antibody that recognizes rat, human and rabbit RBP. A single protein band from the rabbit lacrimal fluid bound the antibody, and this protein comigrated with human RBP which also bound the antibody. We conclude that the lacrimal gland contains RBP mRNA and that the lacrimal gland synthesizes and secretes RBP into the lacrimal gland fluid. This is the first demonstration that an extrahepatic tissue containing RBP mRNA synthesizes and secretes the protein in vivo.
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PMID:The lacrimal gland synthesizes retinol-binding protein. 133 54

A study was conducted to determine the levels of cellular retinol-binding protein (CRBP) mRNA and protein in various tissues of the rat, to explore relationship between CRBP mRNA and protein levels in different tissues, and to examine the effects of changes in retinol nutritional status on the tissue distribution and levels of CRBP mRNA. Previous studies have shown that tissue CRBP protein levels are reduced in totally retinoid-deficient rats, but are otherwise minimally affected by changes in retinoid status. Three groups of male rats were compared: normal controls, retinoid-deficient, and retinol-repleted deficient rats. CRBP mRNA levels were measured by RNase protection assay and CRBP protein levels by radioimmunoassay in seven tissues. High levels of both CRBP mRNA and CRBP protein were found in the proximal epididymis, kidney, and liver; lower levels were seen in lung, testis, spleen, and small intestine. Tissue CRBP mRNA and protein levels were highly correlated (P less than 0.01) with each other. Retinoid deficiency did not alter the levels of CRBP mRNA found in the proximal epididymis, kidney, and liver. In contrast, CRBP mRNA levels in the lung, testis, spleen, and small intestine were reduced substantially in retinoid-deficient rats, to values that were only 23% to 50% of the corresponding values in the tissues of control rats. After oral repletion with retinol (4-18 h earlier), CRBP mRNA levels for these latter four tissues were found to have risen to control or near-control levels. The suggestion is raised that retinol repletion may have directly induced the expression of the CRBP gene in these particular tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cellular retinol-binding protein messenger RNA levels in normal and retinoid-deficient rats. 238 Jun 30

Retinol (vitamin A alcohol), which plays an important role in the differentiation of epithelia, can be transferred to chromatin in vitro. Rat liver chromatin can accept retinol in a specific and saturable manner only when the retinol is presented as a complex with cellular retinol-binding protein (CRBP). A partial characterization of the nuclear components responsible for accepting retinol is reported here. A preparation of solubilized chromatin isolated from liver nuclei was able to accept retinol from its complex with CRBP as described previously for nuclei and chromatin. The binding of retinol to chromatin was noncovalent. However, chromatin prepared from nuclei which were incubated with DNase I or micrococcal nuclease did not accept retinol specifically. Chromatin in the form of mono and dinucleosomes also did not accept retinol. However, treatment of nuclei with RNase did not affect the specific binding of retinol. Furthermore, it has been found that retinol was not transferred to purified double or single stranded DNA. These results are interpreted to indicate that the transfer of retinol to specific nuclear binding sites requires a higher order of chromatin structure than that occurring in nucleosome preparations.
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PMID:Partial characterization of nuclear binding sites for retinol delivered by cellular retinol binding protein. 298 10

Studies were conducted to explore in rats the role of retinol in the regulation of the synthesis and secretion of retinol-binding protein (RBP) by the visceral yolk sac compared to the liver. Previous studies have shown that in retinol deficiency, hepatic RBP secretion is specifically inhibited, whereas hepatic RBP synthesis rate is unchanged. Retinol-depleted, retinoic acid-supplemented female rats were mated, and maternal liver, fetal liver, and visceral yolk sac were obtained at 14 days of gestation (retinol-depleted group). A group of identically treated, retinol-depleted rats were repleted with retinol on the 14th day of gestation, and the same tissues were collected 6 h later (retinol-repleted group). Normal female rats were used as controls. RBP was assayed by radioimmunoassay and RBP mRNA levels by RNase protection assay using a rat RBP cDNA clone. RBP levels in the visceral yolk sac were elevated 10-fold in the retinol-depleted as compared to the control rats and had declined to near normal values in the retinol-repleted animals. The relative levels of RBP mRNA in the visceral yolk sac were very similar in all three groups of rats. Thus, as in the liver, in the visceral yolk sac retinol deficiency inhibits RBP secretion without altering RBP mRNA levels. In the visceral yolk sac, as in the liver, retinol status appears to regulate RBP secretion specifically, without affecting the rate of RBP biosynthesis.
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PMID:Retinol-binding protein synthesis and secretion by the rat visceral yolk sac. Effect of retinol status. 334 35

Elimination of low molecular weight proteins during sequential ultrafiltration/dialysis was studied in 29 uremic patients. Beta-2-microglobulin, retinol binding protein, free light chains lambda and kappa, Zn-alpha-2-glycoprotein, hemopexin, prealbumin, hemoglobin, albumin, acid alpha-1-glycoprotein, haptoglobin, alpha-1-antichymotrypsin, ribonuclease, lysozyme, amylase, non-specific esterase, and proteolytic activity were detected in all ultrafiltrates tested. The level of total protein and ribonuclease was determined in 36 crude ultrafiltrates from 23 patients. Concentrated ultrafiltrates were used to quantitate retinol binding protein, prealbumin, albumin, lysozyme, and amylase. Other proteins identified in the ultrafiltrates are present in trace amounts. The question was discussed whether ++inextensive but systematic loss of proteins during hemofiltration in chronic RDT might be the cause of patient homeostasis disturbances.
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PMID:Detection of plasma proteins during sequential ultrafiltration/dialysis. 406 85

The high-speed supernatant fraction of rat liver, lung, kidney, testis, and intestinal mucosa contains a component capable of binding [(3)H]retinol in vitro when binding is analyzed by sucrose density gradient centrifugation or gel filtration. This binding component can be distinguished from one identified in rat serum. Whereas the tissue component sediments in the 2S region of sucrose gradients, the serum component sediments in the 4.6S region. Molecular weight estimations by gel filtration indicate molecular weights of 16,000 and 67,000 for the tissue and serum binding components, respectively. Unlabeled retinol, but not retinoic acid, competes for the binding of [(3)H]retinol in tissue cytosols. Competition for the binding of [(3)H]retinol by unlabeled retinal has also been observed in tissue cytosols, but may result from the in vitro reduction of retinal to retinol. Unlabeled retinol, retinal, and retinoic acid fail to compete for the binding of [(3)H]retinol in serum under the conditions used. The tissue binding component (testis) is sensitive to digestion with Pronase, but not with RNase or DNase, indicating a protein nature for this component.
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PMID:In vitro binding of retinol to rat-tissue components. 451 41

A retinol dehydrogenase, RoDH(1), which recognizes holo-cellular retinol-binding protein (CRBP) as substrate, has been cloned, expressed, and identified as a short-chain dehydrogenase/reductase (Chai, X., Boerman, M. H. E. M., Zhai, Y., and Napoli, J. L. (1995) J. Biol. Chem. 270, 3900-3904). This work reports the cloning and expression of a cDNA encoding a RoDH isozyme, RoDH(II). The predicted amino acid sequence verifies RoDH(II) as a short-chain dehydrogenase/reductase, 82% identical with RoDH(I). RoDH(II) recognized the physiological form of retinol as substrate, CRBP, with a Km of 2 mM. Similar to microsomal RoDH and RoDH(I), RoDH(II) had higher activity with NADP rather than NAD, was stimulated by ethanol and phosphatidyl choline, was not inhibited by the medium-chain alcohol dehydrogenase inhibitor 4-methylpyrazole, but was inhibited by phenylarsine oxide and the short-chain dehydrogenase/reductase inhibitor carbenoxolone. Northern blot analysis detected RoDH(I) and RoDH(II) mRNA only in rat liver, but RNase protection assays revealed RoDH(I) and RoHD(II) mRNA in kidney, lung, testis, and brain. These data indicate that short-chain dehydrogenases/reductase isozymes expressed tissue-distinctively catalyze the first step of retinoic acid biogenesis from the physiologically most abundant substrate, CRBP.
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PMID:Cloning of a cDNA for a second retinol dehydrogenase type II. Expression of its mRNA relative to type I. 749 45

Cellular retinaldehyde-binding protein (CRALBP) appears to play a role in the vertebrate visual process as a substrate-routing protein, influencing the enzymatic partitioning of 11-cis-retinol at a key branch point in the visual cycle. Genomic clones spanning 29 kilobases and encompassing the human CRALBP gene have been isolated by screening two human genomic libraries and from polymerase chain reaction amplification of human leukocyte DNA. The sequence of 13,647 contiguous nucleotides has been determined, including 3130 and 516 bases from the 5'- and 3'-flanking regions, respectively. The human CRALBP gene exists as a single copy in the genome based on Southern analyses and localization to a single site on human chromosome 15 (Sparkes, R. S., Heinzmann, C., Goldflam, S., Kojis, T., Saari, J. C., Mohandes, T., Klisak, I., Bateman, J. B., and Crabb, J. W. (1992) Genomics 12, 58-62). The gene is composed of eight exons and seven introns with average lengths of 198 base pairs and 1.2 kilobases, respectively, and which exhibit conventional vertebrate splicing. Alu repetitive sequences exist in introns 4 and 5 as well as in the 5'- and 3'-flanking regions of the gene. RNase protection and primer extension analyses indicate that the human CRALBP gene transcription start site is 922 bases upstream of the initiation codon. The first exon is entirely untranslated and both exon 2 and exon 8 contain untranslated regions. The proximal 5'-flanking region lacks GC boxes and consensus TATA and CCAAT boxes at the usual positions. The 3'-untranslated region of CRALBP exon 8 is essentially identical to a partial cDNA clone reportedly isolated from a human hippocampus cDNA library, suggesting that the protein may be expressed in a wider spectrum of tissues than previously recognized. The human CRALBP genomic clones and structure provide valuable tools for studying the physiological role of the protein in vision and visual disorders.
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PMID:Molecular cloning and structural analysis of the human gene encoding cellular retinaldehyde-binding protein. 792 38

Cells that require or metabolize vitamin A contain cellular retinol-binding proteins (CRBP) and cellular retinoic acid-binding proteins (CRABP) which apparently participate in metabolism and transport of retinoids within the cell. Since the lacrimal gland secretes and metabolizes vitamin A, the cellular retinoid-binding proteins and their mRNAs should also be present in this gland. Total RNA from rat and rabbit lacrimal glands was analysed by RNase protection using 32P-labeled antisense cRNA probes. CRBP-I mRNA is present in rat lacrimal gland at 2% of the level in liver but CRBP-I mRNA could not be identified conclusively in rabbit lacrimal gland using the available rat cRNA probe. CRABP-I mRNA is present in rat lacrimal gland at 5% of the level in the 12-day gestation rat fetus, but was not detectable in the rabbit lacrimal gland. Rabbit or rat lacrimal gland cytosol was incubated with [3H]retinol or [3H] retinoic acid followed by ion-exchange chromatography using a Tris buffer and NaCl gradient. CRBP is present in rabbit and rat lacrimal gland at 78.5 +/- 14.5 and 71.1 +/- 11 pmol g-1 protein, respectively. CRABP is present in rat lacrimal gland at 190.6 +/- 13.8 pmol g-1 protein but was not detectable in rabbit lacrimal gland. The presence of CRBP in the lacrimal gland is consistent with its role in secretion of retinol into the lacrimal gland fluid. The apparent lack of CRABP in rabbit lacrimal gland as compared with rat suggests species differences in the role of retinoids in differentiation and maintenance of this organ.
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PMID:Cellular retinol-binding protein and cellular retinoic acid-binding protein in the lacrimal gland. 838 4

The primary and rate-limiting step in retinoic acid (RA) biosynthesis requires the conversion of retinol into retinal. Previously, two genes encoding retinol dehydrogenases (RoDH), which recognize holo-cellular retinol-binding protein as substrate, had been cloned, expressed and identified as members of the short-chain dehydrogenase/reductase (SDR) gene family. This work reports the cloning of a cDNA encoding a third RoDH isozyme, RoDH(III). The deduced amino-acid sequence of RoDH(III) indicates 97.8% identity with RoDH(I) and 82.3% identity with RoDH(II). RNase protection assays revealed RoDH(III) mRNA expression only in rat liver, in contrast to RoDH(I) and RoDH(II), which had their mRNA expressed in rat liver, kidney, lung, testis and brain. These data extend the insight that a subfamily of SDR isozymes, tissue-distinctively expressed, catalyzes the first step in RA biogenesis.
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PMID:Cloning of a rat cDNA encoding retinol dehydrogenase isozyme type III. 864 50


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