Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific receptors for retinol are present in the cytosol fraction of corneal epithelium as demonstrated by sucrose density gradient centrifugation. These appear to be (1) protein in nature (2) of small molecular size (2 S) (3) specific for retinol and (4) present in several species. Assuming a receptor molecular weight of 15 000 and a single mole of retinol bound/mole of receptor protein, the association constant value is 5.26-10(7) with deltaG degrees = -8.53 kcal/mol. 2-S receptors are also observed in stroma and endothelium along with another binding species of approximately 8 S. Binding of [3H]retinol in bovine epithelial cytosol can also be demonstrated by disc gel electrophoresis and gel filtration. Immunodiffusion techniques demonstrate that monkey corneal epithelial and stromal cytosol samples do not contain contaminating serum retinol binding-protein.
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PMID:Retinol receptors in corneal epithelium, stroma and endothelium. 40 47

Vitamin A-transporting protein in chicken plasma was purified by column chromatography on DEAE-Sephadex and Sephadex G-100; the protein formed a complex of retinol-binding protein (RBP) with prealbumin (PA). The molecular weight of the 1:1 molar complex was estimated to be 76,000 by gel filtration, and the sedimentation coefficient (S20,W) was found to be 5.2 S. RBP and PA were dissociated from the purified complex by means of CM-Sephadex column chromatography. Purified RBP contained 1 mole of vitamin A bound per mole of RBP. The molecular weight of RBP was determined to be 20,000 by gel filtration on Sephadex G-75, 19,000 by SDS-disc gel electrophoresis, and 20,500 by sedimentation equilibrium analysis. The S20,W was calculated to be 2.0 S. The molecular weight of PA was determined to be 56,000 by gel filtration, 52,000 by sedimentation equilibrium analysis, and 13,000 by SDS-disc gel electrophoresis. The S20,W was calculated to be 3.9 S. From these findings it was concluded that PA consists of four subunits, each with a molecular weight of approximately 13,000. Peptide mapping experiments suggested that the subunits were identical. No carbohydrates were detected in either RBP or PA. Chicken RBP and PA were immunologically distinct from those of human and rat. It is well established that vitamin A is transported bound to a specific plasma protein, retinol-binding protein (RBP), in both man (1,2) and rat (3). Purified human and rat plasma RBP have a single binding site for one molecule of retinol, alpha mobility on disc gel electrophoresis, and a molecular weight of approximately 20,000. In both species, RBP forms a tight complex with plasma prealbumin (PA) and normally circulates as a 1:1 molar protein-protein complex with PA (1-5). Despite these similarities, no immunological cross-reactivity between human and rat RBP has been observed (3,6). The present study was undertaken to explore whether or not a similar transport system for vitamin A exists in the chicken, a nonmammalian vertebrate. During the course of this study, Mokady and Tal (7) reported the isolation of RBP from chicken plasma and some physicochemical properties, e.g., a molecular weight of about 19,000. On the other hand, Muto, Smith, and Goodman (6) had already observed that the molecular weight of vitamin A-containing protein in fresh chicken plasma is approximately 60,000-80,000, as determined by gel filtration. However, no convincing information is available regarding an entire system of vitamin A transport in chicken plasma. We now describe procedures for the isolation of the RBA-PA complex of chicken plasma and the dissociation into the component proteins, RBP and PA. We also describe in detail the physicochemical properties of the individual proteins. It is also clearly demonstrated that chicken RBP and PA are immunologically distinct and different from the respective proteins in man and rat. Moreover, purified chicken PA appears to be a tetramer of four identical subunits and is thus similar to human and rat PA.
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PMID:Vitamin A transport in chicken plasma: isolation and characterization of retinol-binding protein (RBP), prealbumin (PA), and RBP--PA complex. 80

Associations were sought between prevalence of nevi on the arms and other variables in controls from a case-control study of cutaneous malignant melanoma. The prevalence of nevi was higher in women than men, fell with age up to about 35 years of age, and was low in those born outside Australia. Among pigmentary characteristics, there was strong evidence only of an association with skin color of the upper inner arm. The highest prevalence of nevi was in those with skin of intermediate darkness. Peak prevalence of nevi was also seen in intermediate categories of variables indicating sun exposure, particularly mean annual hours of bright sunlight at places of residence when 10-24 years of age, total outdoor exposure time per week in the summer at 10-24 years of age, and usual summer suntan on the arms in the last 10 years. These dose-effect patterns may indicate conflicting effects of sun exposure on appearance and disappearance of nevi. The protective effect of birthplace outside Australia appeared to be due to the corresponding low mean annual hours of bright sunlight at places of residence when 10-24 years of age. The prevalence of nevi was comparatively lower in those who drank alcohol and in those who had average or high daily intakes of retinol. These associations were not explained by those of any of the other variables.
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PMID:Etiology of common acquired melanocytic nevi: constitutional variables, sun exposure, and diet. 346 Nov 95

Biochemical and immunological techniques were used to determine the emergence of interstitial retinol binding protein (IRBP), rhodopsin, and stored retinyl esters (all-trans and 11-cis) during retinal development in normal and rd mice. IRBP could be demonstrated at embryonic Day 17 (E17), corresponding to an early stage of inner segment development. Although all-trans retinyl esters were present earlier, 11-cis retinyl esters did not appear until postnatal Days 6-7 (P6-P7), corresponding to rod outer segment (ROS) disc formation. Rhodopsin was detected at the same developmental stage. The proportion of 11-cis retinyl esters reached a maximum of 40-50% at P15-P20. Thereafter, the proportion dropped, due to more rapid accumulation of the all-trans isomer. Rhodopsin and IRBP increased in parallel with ROS elongation up to P25, when the ROS had reached their mature lengths. The increases then continued up to P40-P50. In rd (retinal degeneration) mice, IRBP and rhodopsin were identical with the controls until P12, but then dropped as the photoreceptors degenerated. Synthesis and secretion of IRBP in vitro was less than 10% of the controls in rd retinas at P26, when only 4-5% of the photoreceptors survived. The quantities of retinyl esters (mainly stearate and palmitate in the ratio of 6:1, respectively) stored in dark-adapted mouse eyes progressively increased as the animals aged, representing 0.5 mole eq. of the rhodopsin at 8 months. Although retinyl esters (11-cis and all-trans) also accumulated in rd mouse eyes up to P12, little further increase occurred. At P93, the retinyl esters (0.01 nmole X eye-1) were only 4% of the controls at P91. A peak in the proportion of 11-cis isomer occurred at P10-P20, but it averaged only 15% of the total ester and declined to 5% at P93. These findings support the hypothesis that IRBP is synthesized by the rods and cones, and suggest that its synthesis and secretion are initiated when the photoreceptor inner segments start to differentiate. 11-cis Retinoids and rhodopsin do not appear until the outer segments start to form. It is suggested that in the rd mouse the absence of photoreceptors, perhaps coupled with lack of normal interphotoreceptor matrix, leads to a loss in the ability of the pigment epithelium to store retinyl esters.
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PMID:Rhodopsin, 11-cis vitamin A, and interstitial retinol-binding protein (IRBP) during retinal development in normal and rd mutant mice. 373 15

The content of retinol and ascorbic acid in blood plasma and lymphocytes of colonic cancer patients was 2-3 times as reduced as compared to that in donors. The beta-carotene content in the patients' blood plasma did not show any statistical changes. The low content of vitamins A and C in the plasma correlated in the same patients with inhibition of the cell proliferative response to alloantigens in a mixed lymphocyte culture and with a reduction in the lymphocyte response to the T cell mitogen ConA. The proliferative activity of lymphocytes stimulated with the B cell mitogen PWM was lowered in patients insignificantly. The blood plasma retinol was measured by high-pressure liquid chromatography, with the use of C19-retinoid as an internal reference. The beta-carotene content was measured by a combination diffusion laser spectrometer, Mole-77.
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PMID:[Plasma retinol, beta-carotene and ascorbic acid levels and functional activity of lymphocytes in patients with large intestine cancer]. 633 21

The amount, distribution, and composition of vitamin A stored in the eyes of 29 postmortem donors was determined by a combination of techniques, including high-pressure liquid chromatography. The vitamin A concentration in the pigment epithelium-choroid (RPE-Ch) was the highest observed for human non-liver tissue and amounted to 7.9 +/- 4.3 nmol/eye (n = 28), or 10.4 +/- 7.1 microgram/gm (n = 27). There was no evidence for significant losses during the interval between death and enucleation or during subsequent storage at 4 degrees C. The vitamin A extracted from the retina was 15.3% of that in the corresponding RPE-Ch. By measuring rhodopsin regeneration in retinal homogenates incubated with 11-cis retinal, we estimated that the amount of vitamin A in the RPE-Ch of fully dark-adapted eyes would represent 2.5 mole equivalents of the retinal rhodopsin, a value similar to that found in the frog. A preponderance of the vitamin A in the eye was esterified (98.3% in the RPE-Ch, 79.3% in the retina) and consisted principally of stearate and palmitate in the ratio of 1:4.8. A small amount of oleate was also detected. The ratio of 11-cis isomer over the all-trans averaged 1.52 +/- 0.48 (n - 11). Variable, usually small proportions of 13-cis retinyl esters were also present. Intact RPE-Ch or isolated RPE cells esterified exogenous all-trans-3H2-retinol to the same fatty acids in roughly the same proportions as in the endogenous stores. The all-trans configuration was mainly retained during uptake and esterification, although some isomerization to 13-cis also occurred. No 11-cis isomer was formed under these conditions.
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PMID:Vitamin A in human eyes: amount, distribution, and composition. 707 16

beta-Lactoglobulin (Big) binds 1 mol of a fatty acid spin-label analog, 5-doxylstearic acid (5-DSA), per mole of protein with a dissociation constant Kd = 0.8 microM for the strongest binding site. There are also several weaker sites for this ligand. Blg saturated with either retinol or retinoic acid binds 5-DSA with essentially equal affinity (Kd = 0.6 and 1 microM, respectively). Palmitic acid and SDS displace bound 5-DSA from Blg. However, unlike palmitic acid, 5-DSA binding does not enhance the structural stability of Blg to urea denaturation. The spin-labeled fatty acid also binds to the protein at low pH, presumably at secondary fatty acid binding sites. These results suggest that Blg binds at least two different types of hydrophobic ligands simultaneously.
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PMID:Fatty acids and retinoids bind independently and simultaneously to beta-lactoglobulin. 904 77

Native beta-lactoglobulin (Blg) binds 1 mole of palmitic acid per mole of protein with a dissociation constant of 0.6 microM for the primary fatty acid binding site. Chemical modification of Cys 121, which lies at the external putative hydrophobic binding site of Blg, does not affect retinol or 4,4'-bis 1-(phenylamino)-8-naphthalenesulfonate (bis-ANS) binding to the protein, indicating that the incorporated appendages do not perturb the internal hydrophobic site within the beta-barrel of Blg (i.e., the retinoid site is unaffected). On the other hand, methylation of Cys 121, reduces the affinity of Blg for palmitic acid by 10-fold as monitored by intrinsic fluorescence. Modification of the Cys 121 with methylmethanethiosulfonate or a thiol-specific spin label appears to either further weaken or totally eliminate fatty acid binding, respectively, due to steric hindrance. Furthermore, this binding pattern has been independently verified using a spin labeled fatty acid analog and monitoring ESR as well as by bis-ANS fluorescence when bound to the protein. These results suggest that fatty acids bind at the "external site" of beta-lactoglobulin, between the sole alpha-helix and the beta-barrel. In addition, structural stability studies of native and chemically modified Blg appear to confirm this observation as well.
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PMID:Mapping fatty acid binding to beta-lactoglobulin: Ligand binding is restricted by modification of Cys 121. 951 70

The purpose of this study was to investigate the dispersal mechanism of retinol (Vitamin A, VA) into phospholipid. VA was dispersed with soybean phosphatidylcholine (PC) using sonication and the dispersal mechanism was evaluated by characterizing the dispersed particles using dynamic light scattering, fluorescence spectroscopy and surface monolayer techniques. The dispersions in the VA mole fraction range of 0.1-0.7 were stable at room temperature for 3 days. A limited amount of VA was incorporated into PC bilayer membranes (approximately 3 mol%). The excess VA separated from the PC bilayers was stabilized as emulsion particles by the PC surface monolayer. When the PC content was less than the solubility in VA (mole fraction of VA: more than 0.8), the PC monolayer did not completely cover the hydrophobic VA particle surfaces. In the case, the particle size increased drastically and the separation into oil/water occurred. The miscibility between VA and PC and the lipid composition were critically important for the stability of the dispersed particles (coexistence of emulsion particles (surface monolayer of PC+core of VA) with vesicular particles (bilayer)) of the lipid mixtures.
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PMID:Formation of the dispersed particles composed of retinol and phosphatidylchiline. 1259 40

The major component of the whey fraction of bovine milk, beta-lactoglobulin (betaLG), has been transformed by grafting polyethylene glycol chains either on the thiol group (free and after reduction of the S-S bridges) of the cysteine residues, or on the amino group of the lysine residues and/or of the N-terminal amino acid. Acylation of the protein was achieved at a controlled pH of 7.0 using increasing ratios of activated PEG to betaLG. Transformation of the dimeric form into the monomer occurred at least for the fully pegylated adduct. The number of polymer chains fixed per mole of protein was determined by dosage of the free amino functions still present after reaction. The incidence of pegylation on the secondary structure of betaLG was evaluated using the Fourier Transform Infrared Spectroscopy (FTIR). Denaturation studies with guanidinium hydrochloride (Gu-HCl) by means of spectrofluorimetric measurements, showed an identical behavior of native as well as of pegylated betaLG.The antigenicity of the fully pegylated adduct was examined through antigenic competition towards native betaLG. The pegylated protein exhibited less than 1/100 of the native betaLG inhibition capacity, that could moreover never be complete. This is thus demonstrating the loss of accessibility for at least multiple conformational epitopes through pegylation procedure.Spectrofluorimetric measurements showed that betaLG-N-PEG(7) was still able to bind retinol while no effect on the intrinsic fluorescence could be detected by adding palmitic acid. Whether this last ligand binds or not to pegylated betaLG is discussed.
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PMID:Preliminary characterization of bovine beta-lactoglobulin after its conjugation to polyethylene glycol. 1863 71


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