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Biomedical subjects

J C Saari

Publications and source records attributed to J C Saari.

At least 73 records · Page 4Linked to original sources
PubMed1979

11-cis-Retinal-binding protein from bovine retina. Isolation and partial characterization.

11-cis-Retinal-binding protein from bovine retina has been purified to apparent homogeneity by gel filtration ion exchange, and hydroxylapatite chromatography. The molecular weight determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 33,000. A value of 36,000 was obtained by gel filtration. With 11-cis-retinal bound to the protein a bleachable spectral peak with maximum absorption at 425 nm was observed. When isolated without addition of exogenous retinal the purified binding protein displayed absorbance maxima at 340 and 425 nm, indicating the occurrence of two ligands in addition to the typical protein absorbance. The endogenous ligands responsible for these maxima were tentatively identified as 11-cis-retinol and 11-cis-retinal, respectively. The binding protein did not cross-react with antibodies prepared against bovine opsin, and its amino acid composition was distinct from that of opsin. The amount of retinal-binding protein extracted was approximately 1 nmol/retina or 1 mol of binding protein/20 mol of opsin. Its specificity and relative abundance suggest that the 11-cis-retinal-binding protein may play a major role in the visual cycle.

Amino Acids↗
PubMed1978

Cellular retinol- and retinoic acid-binding proteins in transformed mammalian cells.

Extracts prepared from several lines of transformed cells were examined for the presence of cellular binding proteins specific for retinoids. Extracts of human retinoblastoma cell line WERI-Rb1 contained a cellular binding protein specific for retinoic acid, whereas extracts of human retinoblastoma cell line Y-79 contained cellular binding proteins for both retinol and retinoic acid. Upon purification, the latter two binding proteins proved to have properties similar to those of the corresponding proteins obtained from bovine retina. Smaller amounts of these binding proteins were detected in extracts of undifferentiated and differentiated neuroblastoma and McCoy cells. HeLa and rat glioma cells had no detectable amount of binding proteins. The 11-cis-retinal-binding protein, present in extracts of human, rat, and bovine retina, was not found in any of the cell lines examined.

Animals↗
PubMed1977

Occurrence of a binding protein for 11-cis-retinal in retina.

A binding protein for retinal has been found in the soluble protein fraction of bovine retina. It was separable from the intracellular retinol- and retinoic acid-binding proteins by gel filtration on Sephadex G-100 and appeared to have a molecular weight of about 50,000. The new binding protein did not bind retinol or retinoic acid. The binding protein neither oxidized retinal in the presence of reduced pyridine nucleotides and is presumed, therefore, not to be a dehydrogenase. Bound retinal was reduced to retinol in the presence of liver alcohol dehydrogenase and NADH, indicating that the functional group remained accessible when in the protein complex. The binding protein bound cis isomers of retinal preferentially. Bound ligand was displaced most effectively by 11-cis-retinal. When individual cis-trans isomers of retinal were presented to the binding protein, binding was maximal with the 11-cis isomer. It is proposed that the protein be referred to as 11-cis-retinal-binding protein.

Alcohol Oxidoreductases↗
PubMed1977

Occurrence of 11-cis-retinal-binding protein restricted to the retina.

A binding protein for retinal (vitamin A aldehyde), the 11-cis-retinal-binding protein, was present in the soluble protein fraction of rat retina but was absent from brain, lung, heart, skeletal muscle, liver, kidney, spleen, small intestine, and testes. The binding protein was also found in human retina but not human liver. The binding protein for retinal from human retina did not bind retinol and was larger than, and readily separable from, the cellular retinol-binding protein which did not bind retinal. It would appear that the occurrence of a soluble binding protein for retinal, unlike the more widely distributed binding proteins for retinol and retinoic acid, may be unique to the retina.

Animals↗
PubMed1977

Localization of cellular retinal-binding protein in bovine retina and retinal pigment epithelium, with a consideration of the pigment epithelium isolation technique.

Bovine RPE was isolated by commonly used brushout procedures and analyzed by light and electron microscopy. The preparation was found to consist almost entirely of cells with retained organelles (mitochondria, pigment, and other granules) but with broken surface membranes and extracted cytoplasm. In keeping with this, the wash obtained by sedimenting these broken cells contained approximately 97 percent of the cellular retinol-binding protein present in the suspension. Cellular retinoic acid-binding protein, present in bovine retinal extracts, was found in low amounts in the wash from RPE. The cellular retinol-binding protein present in the RPE wash was of high specific activity and similar in properties to that obtained from bovine retina. Supernatant obtained from sonicated rod outer segments contained approximately 10 percent of the retinol-binding protein of the retina. No retinoic acid-binding protein was found. The relatively large amount of cellular retinol-binding protein present in the RPE (more than is found in the retina) is consistent with a functional role of this protein in uptake and transport of retinol by the RPE.

Animals↗
PubMed1976

Separable binding proteins for retinoic acid and retinol in bovine retina.

Binding proteins for retinoic acid and retinol were separated from a supernatant prepared from bovine retina. Fraction IV from DEAE-cellulose chromatography bound exogenous [3H] retinoic acid which could not be effectively displaced by retinol, retinal, retinyl acetate or palmitate, but which was readily displaced with excess retinoic acid. [3H] Retinol was bound by fraction V from DEAE-cellulose chromatography and was not displaced by retinal, retinoic acid, retinyl acetate or retinyl palmitate, but was readily displaced by excess retinol. Unlike bovine serum retinol-binding protein, neither intracellular binding protein formed a complex with purified human serum prealbumin. The supernatant from bovine retinas was estimated to contain five times more retinoic acid binding than retinol binder.

Animals↗
PubMed1976

Retinol- and retinoic acid-binding proteins: occurrence in human retina and absence from human cultured fibroblasts.

Low-molecular-weight retinol- and retinoic acid-binding proteins were shown to be present in the soluble fraction of human retinal tissue but absent from human fibroblasts grown in tissue culture. By the use of gel filtration and comparison with bovine retinal tissue, the human intracellular binding proteins were found to have molecular weights of approximately 17,000 daltons, which are comparable to the molecular weights of bovine intracellular binding proteins. The quantity of retinoic acid bound exceeded that of retinol by about eightfold.

Animals↗
PubMed1974

The accessibility of bovine rhodopsin in photoreceptor membranes.

Bovine photoreceptor membranes have been treated with proteases to determine the accessibility of rhodopsin to these large, water soluble molecules. The polypeptides that remain associated with the membranous structure after proteolysis were detected by sodium dodecyl sulfate gel electrophoresis. Thermolysin and chymotrypsin degraded rhodopsin (apparent mol wt 35,000-36,000) to fragments of 29,000 and 23,000 apparent mol wt, respectively, without affecting the chromophoric absorption of the molecule or removing the region of the polypeptide carrying carbohydrate. The two fragments were isolated and their amino acid compositions were determined. They do not appear to be more hydrophobic than rhodopsin. Subtilisin, at low concentration and temperature, produced a fragment with the same molecular weight as that produced by thermolysin. At higher concentrations, subtilisin yields major fragments of mol wt 23,000 and 20,000 without affecting the chromophoric absorption. Two intermediate fragments of apparent mol wt 29,000 and 26,000 were detected during the course of this degradation. Carbohydrate is retained by all but the smallest fragment. Bleaching of the photoreceptor pigment did not appreciably alter any of the fragmentation patterns. Trypsin did not alter the molecular weight of rhodopsin under the conditions of this study. Approximately 35-45% of rhodopsin appears to be accessible to the aqueous environment and can be removed without affecting the chromophoric properties of the retinaldehyde-carrying region which remains bound to the membrane.

Amino Acids↗