Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The spectral difference between normal and rapidly reacting deoxyhemoglobin (Sawicki and Gibson (1976), J. Biol Chem. 251:1533-1542) is used to study the relationship between CO binding to hemoglobin and the conformational changes to the rapidly reacting form in a combined flow-laser flash experiment. In both pH 7 phosphate buffer and pH 7 bis(2-hydroxy-ethyl)imino-tris (hydroxymethyl)methane buffer (bis-Tris) with 500 muM 2,3-diphosphoglycerate (DPG), the conformational change lags far behind CO binding; rapidly reacting hemoglobin is not observed until more than 10% of the hemoglobin is liganded. In pH 9 borate buffer the formation of rapidly reacting hemoglobin leads CO binding by a significant amount. A simple two-state allosteric model (Monod et. al. (1965), J. Mol. Biol. 12:88-118) which assumed equivalence of the hemoglobin subunits in their reaction with CO was used to simulate the experimental results. In terms of the model, the conformational change lead observed at pH 9 suggests that significant conformational change has occurred after binding of only one CO molecule per tetramer. In the presence of phosphates good agreement between experimental results and simulations is obtained using parameter values suggested by previous experimental studies. The simulations suggest that the conformational change occurs after binding of three CO molecules.
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PMID:The relation between carbon monoxide binding and the conformational change of hemoglobin. 3 Apr 92

The myoglobin-like haemoprotein leghaemoglobin (Lb I) from lupine root nodules has a great affinity to molecular oxygen and seems to be involved in O2-transport. Some ligands of low molecular weight are supposed to affect the haemoglobin (Hb) and myoglobin (Mo) function in O2-transport. To investigate this possibility for lupine Lb I, the affinity of this protein to cyanide (CN-), azide (N3-), fluoride (F-), thiocyanate (NCS-), imidazole (Im), nicotinic acid (NA), acetic acid has been investigated, using: 0.05 M MES, pH 5.2-6.5; 0.1 M Na-phosphate in 0.05 M Tris-buffer, pH 6.5-9.0. The affinity for Lb I to N3-, CN-, F- and NA (the Bohr effect) was found to be pH-dependent. The values of PK ionization for the groups affecting the ligands binding were determined. The positive correlation between the ligand affinity and the ligand power was found. Lb I appears to have the greatest ligand affinity constants when compared with other haemoproteins of this class.
Mol Biol (Mosk)
PMID:[Lupine leghemoglobin affinity to ligands. The effect of pH and buffer nature]. 3 94

The condition of methylviologen photoreduction by chloroplasts was investigated. Argon bubbling through the suspension of chloroplasts or degasing in vacuum caused inhibition of methylviologen reduction probably due to the denaturation of chloroplast membranes at the water/air boundary. Adding glycerol or bovine serum albumine or removing oxygen from chloroplast suspension with the aid of the oxygen absorbing-systems preserved the activity of chloroplasts. Methylviologen photoreduction is inhibited by DCMU (10(-7) M) and Tris-buffer treatment and is activated by uncouples. The pH-dependence is similar to that of the Hill reaction. Triton X-100 (0.007%), ethyl ether (2%) and heating up to 42 degrees activated the Hill reaction but inhibited methylviologen reduction. Water molecule probably acts as an initial electron donor in this reaction. It is proposed that the steady level of methylviologen photoreduction is determined by a relationship between the rate of methylviologen electron acceptance and cyclic electron flow short-circuiting photosystem I.
Mol Biol (Mosk)
PMID:[Methylviologen photoreduction by chloroplasts]. 3 95

Nuclear ribonucleoprotein (RNP) complexes that contain the U1 and U2 RNA of chromatin of Novikoff hepatoma cells were extracted with 0.01 M Tris-HCl (pH 8.0) after the nuclei were initially washed with 0.075 M NaCl and 0.025 M EDTA (pH 8.0). These RNP complexes were purified by chromatography on Sepharose 6B columns and centrifugation on sucrose density gradients. The identity of the U1 and U2 RNA in these particles was established by their electrophoretic mobility in polyacrylamide gels and their T1 RNase fingerprints which were identical with those of authentic U1 and U2 RNA (R. Reddy et al. (1974), J. Biol. Chem.249, 6486-6494; H. Shibata et al. (1974), Mol. Cell. Biochem. 4, 3-19). The nuclear riboncleoproteins had a buoyant density of 1.47 g/ml in CsCl gradients. Two-dimensional polyacrylamide gel electrophoresis of their proteins showed these RNP complexes contain 10 polypeptide spots, of which two are phosphorylated in vivo.
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PMID:Nuclear ribonucleoprotein complexes containing U1 and U2 RNA. 16 94

Conditions were worked out for maximal stabilization of dexamethasone binding activity of rat liver cytosol in the absence of the protective steroid ligand. Important stabilization factors are ionic strength, thiol-protecting agents, glycerol and pH. Maximal stability of the cytosol is observed in a buffer consisting of 20 mM Tris-HCl, pH 7.5, 50 mM KCl, 25 mM beta-mercaptoethanol and 20% glycerol. Chromatography of cytosol on DEAE-cellulose revealed the existence of three dexamethasone receptors, binder DE-1, present in the flow-through fraction and binders DE-2 and DE-3, eluting from the column with salt concentrations of 100 and 190 mM, respectively. Binders DE-2 and DE-3 are not adsorbed on phosphocellulose at pH 7.5, whereas binder DE-1 is. All three receptors are retained to varying degrees on DNA-cellulose columns: binder DE-1 is eluted with salt concentrations of 270 mM, whereas binders DE-2 and DE-3 are eluted between 180 and 200 mM NaCl. The dexamethasone receptors also bind natural glucocorticoids, but to varying degrees, the highest binding being observed to binder DE-2. The receptors obtained after chromatography on DEAE-cellulose, but not on phosphocellulose, cannot be to an appreciable extent charged with dexamethasone.
Mol Cell Endocrinol
PMID:Stabilization and characterization of the dexamethasone-binding proteins in rat liver cytosol. 18 77

Iodoacetamide, N-ethylmaleimide, p-hydroxymercuribenzoate (p-MB) and HgCl2 were tested as inhibitors of microsomal glucose-6-phosphatase. Iodoacetamide had no effect at 2 mM. N-ethylmaleimide inhibited only crude, but not purified microsomal preparations (M2) or crude microsomes exposed to deoxycholate. 14C-labelled N-ethylmaleimide was not bound by the M2 protein fraction. p-MB inhibited all types of preparations and the inhibition was not counteracted by detergent. A more detailed study was carried out with the purified M2 fraction (specific activity: 2-4 mumoles Pi/min/mg protein). Glucose-6-phosphate hydrolysis was inhibited 50% by 5 X 10(-5) M p-MB. The inhibition was completely reversible by dithiothreitol except when the enzyme was pre-incubated with p-MB in the absence of substrate. Then p-MB accelerated the temperature-dependent inactivation of glucose-6-phosphatase. Binding studies showed that around 3 mumoles 14C-p-MB were incorporated into 100 mg M2 protein regardless of the concentration of mercurial in the incubation mixture. That is, over a 25 fold range of p-MB concentration, causing up to 80% inhibition of enzyme activity, no difference was seen in the amount of labelled p-MB which was irreversibly bound to M2 protein. Kinetically p-MB behaved like a reversible inhibitor and this was confirmed by dilution experiments. Several compounds, including some amino acids, antagonized the inhibition by p-MB. The order of effectiveness was EDTA greater than barbital greater than tryptophan greater than histidine greater than lysine greater than other amino acids. Glycine, Tris and urea were ineffective competitors of p-MB inhibition. Double reciprocal plots showed that the Km for glucose-6-phosphate was increased and the Vmax reduced in the presence of p-MB. HgCl2 was a more effective inhibitor than p-MB with a Ki of 6 X 10(-6) M. We conclude that a reaction of p-MB with M2 sulfhydryls does not play a part in the inhibition of enzyme activity. It is suggested that p-MB may interact with one or more amino acid side chains in such a way that enzyme conformation is altered.
Mol Cell Biochem 1976 Jul 30
PMID:The effect of p-hydroxymercuribenzoate and congeners on microsomal glucose-6-phosphatase. 18 75

A DE filter disk technique for assaying the activity of nucleotidase is described. This method is based on the observation that nucleotides bind to the filters at 5 mM Tris-HCl (pH 7.8) while nucleosides do not. As parameter for the nucleotidase activity the decrease of bound nucleotides is determined. In parallel experiments the amount of the product (nucleoside) formed can be measured by DEAE Sephadex column chromatography. The filter disk technique can be applied for the determination of vmax and Km of a nucleotidase by using different ribonucleosidase monophosphate substrates.
Mol Biol Rep 1977 Sep
PMID:Filter paper disk techniques for assay of nucleotidase. 56 67

1. Specimens of human duodenal mucosa were obtained at duodenotomy. Superficial mucosal scrapings were homogenized in isotonic sucrose solution and fractionated by differential centrifugation. The distribution of organelles among the subcellular fractions was monitored by assay of suitable marker enzymes. 2. Enterokinase was recovered predominantly in the nuclear+brush-border fraction and 80% of the total activity was found to be particulate; approximately 20% of the enzyme was present in the soluble fraction, compared with 1% of the brush-border markers sucrase and alkaline phosphatase. 3. The brush-border-containing fraction was subfractionated by treatment with hypertonic Tris followed by differential and density gradient centrifugation. Enterokinase was distributed among the subfractions in parallel with brush-border markers and was concentrated in a subfraction which was highly enriched in microvillous membranes. 4. It was concluded that enterokinase is localized primarily to the microvillous membrane of the epithelial cell brush border in man, but that in addition a proportion of the enzyme may be present in a soluble or easily released form in the duodenal mucosa.
Clin Sci Mol Med 1977 Dec
PMID:Subcellular localization of enterokinase in human duodenal mucosa. 58 40

Human urinary Tamm-Horsfall glycoprotein, which contains 28% carbohydrate, has a monomeric molecular weight of about 80,000 but is isolated from urine in the form of intertwining helical suprastructures with molecular weights greater than 10(7). The native glycoprotein was dissociated and denatured with 6 M guanidinium chloride and was subsequently renatured by dialysis against a Tris-HCl buffer. Using sedimetation equilibrium, the renatured glycoprotein was characterized by a Mw cell of 256,800 and a Mz cell of 356,000. The ratio, Mz/Mw, of 1.39 indicates some polydispersity with regard to molecular size. There was no evidence of helical suprastructures in the renatured glycoprotein as judged by electron microscopy. Ca2+ concentrations of up to 50 mM failed to precipitate the renatured glycoprotein; in contrast, the native glycoprotein is precipitated by Ca2+ concentrations between 5-10 mM. The circular dichroic spectrum of renatured Tamm-Horsfall glycoprotein was obtained, resolved, and tentative band assignments made. The spectrum, which is quite similar to that of native Tamm-Horsfall glycoprotein, exhibited negative extrema at 269 nm (due in large part to disulfides and tyrosines) and at 215 nm (due to protein beta-structure and the N-acetylated hexosamines). The alpha-helical content of the glycoprotein was estimated to be no more than 10% and the amount of beta-structure to be about 33%; these values were not affected by the presence of Ca2+ (1 mM). A glcopeptide fraction (ca. 90% carbohydrate), prepared by extensive pronase digestion of the reduced, S-carboxymethylated glycoprotein, exhibited an ellipticity extremum at 212 nm of + 4,750 deg-cm2/dmole, referred to the concentration of (N-acetylated) hexosamines and neuraminic acid.
Mol Cell Biochem 1977 Apr 12
PMID:Circular dichroism of human urinary Tamm-Horsfall glycoprotein. 89 29

The parameters of fluorescence spectra of myosin and its subunits in Tris-HCl-buffer (pH 7.2) were studied. Analysis of the experimental results of myosin fluorescence quenching with I-ions and the quantum yield of the fluorescence at the excitation wavelength 296 nm shows that the greater part of the tryptophan residues (21 out of 28) is located in the hydrophylic environment. Concentrated solutions of NaCl and KCl do not affect myosin fluorescence, while LiCl, which changes the quaternary structure of the protein, brings about a change in the parameters of the myosin fluorescence spectra. This may be linked with structural changes accompanying the dissociation of the ligh subunits of myosin in the presence of LiCl.
Mol Biol (Mosk)
PMID:[Fluorescence of myosin and its subunits in concentrated salt solutions]. 121 99


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