scholarly journals The properties of subunits of avidin coupled to Sepharose

1973 ◽  
Vol 133 (4) ◽  
pp. 687-698 ◽  
Author(s):  
N. Michael Green ◽  
E. John Toms
Keyword(s):  
Spatial Distribution ◽  
Binding Sites ◽  
Binding Capacity ◽  
Similar Rate ◽  
Guanidinium Chloride ◽  
Temperature Dependent ◽  
Low Concentrations ◽  
Biotin Binding ◽  
Covalently Linked ◽  
Sepharose 4B

Avidin that had been coupled to Sepharose 4B activated with CNBr retained over 90% of its biotin-binding capacity. When low concentrations of CNBr were used about 75% of the protein could be removed from the Sepharose by washing with guanidinium chloride (6 m). The remaining 25%, the covalently bound subunits, had an almost undiminished capacity for biotin but a decreased affinity. Addition of avidin subunits in guanidinium chloride to the coupled subunits followed by dilution or dialysis restored the original biotin-binding capacity and affinity. Three classes of binding sites were present in preparations of the subunits. About 25% were weak (K=5X10−8m), about one third exchanged their biotin in a few minutes (K∼10−10m) and the remainder were indistinguishable from the native tetramer. The last-named exchanged their bound biotin at a similar rate at pH5 and at pH2, they did not lose their biotin in 6 m-guanidinium chloride and they were resistant to tryptic digestion in the absence of biotin. The proportion of these stable sites could be increased to 65% when the subunits coupled to Sepharose were incubated at 37°C. This increase was reversed by guanidinium chloride, which suggested that it was caused by a temperature-dependent association of covalently linked subunits. This in turn implies a temperature-dependent mobility of the agarose matrix of the Sepharose. Analysis of the spatial distribution of subunits within the Sepharose beads led to the conclusion that the association of subunits implied that they could move through distances greater than 20nm (several hundred Å). This mobility and consequent formation of tetramer was greatly decreased when avidin subunits were coupled to Sepharose that had been cross-linked with divinyl sulphone.

scholarly journals Factors affecting the binding of [3H]adenosine 3′:5′-cyclic monophosphate to protein kinase from bovine adrenal cortex

1977 ◽  
Vol 161 (3) ◽  
pp. 653-665 ◽  
Author(s):  
S O Døskeland ◽  
P M Ueland ◽  
H J Haga
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Adrenal Cortex ◽  
Binding Sites ◽  
Binding Capacity ◽  
Binding Assays ◽  
Factors Affecting ◽  
Binding Characteristics ◽  
Standard Curve ◽  
Low Concentrations

Inorganic salts, several proteins and traces of protein precipitants were tested to find out by what mechanisms they modulate the binding of cyclic [3H]AMP to protein kinase (ATP-protein phosphotransferase; EC 2.7.1.37). The separation of free and bound cyclic AMP by (NH4)2SO4 precipitation was unaffected by the above agents and was more reliable than the Millipore filtration technique. Several binding sites for cyclic AMP were revealed in adrenal-cortex extract. When this extract was used as binding reagent in an assay for cyclic AMP, the standard curve was distorted in the presence of KCl because the salt affected the different binding sites to a varying extent. At high ionic strenth the protein kinase isoenzyme I dissociated and showed an extraordinarily high affinity for cyclic AMP. Trichloroacetate and perchlorate at very low concentrations were able to dissociate the protein kinase and modulate its binding characteristics as well. A progressive decrease in the cyclic AMP-binding capacity occurred on prolonged incubations. The binding protein was protected against inactivation by 2-mercaptoethanol, EDTA and several proteins. It was more resistant to denaturation when complexed to cyclic AMP. The enhancement of cyclic AMP binding by bovine serum albumin was investigated in some detail and appeared to be a pure stabilizing effect. It is proposed that the competitive-binding assays for cyclic AMP based on protein kinase be conducted at high ionic strength and in the presence of stabilizers (protein, EDTA, 2-mercaptoethanol). The interference from agents that may dissociate the protein kinase or influence its stability will thus be decreased.

scholarly journals Purification and Metabolism of Rat Antithrombin III

1977 ◽  
Author(s):  
S. Okuda ◽  
M. Nakagawa ◽  
T. Okada ◽  
K. Sawada ◽  
H. Ijichi
Keyword(s):  
Free Radicals ◽  
Binding Sites ◽  
Antithrombin Iii ◽  
Binding Capacity ◽  
Experimental Results ◽  
Affinity Column ◽  
At Iii ◽  
The Difference ◽  
Rat Tissue ◽  
Sepharose 4B

The previously reported heparin sepharose affinity column has been proved to be reduced in its recovery on the repeated uses because of loose binding of ligand to sepharose. We tried to obtain the better recovery of antithrombin III (AT-III) using four different affinity columns of CNBr activated sepharose 4B, AH-sepharose 4B, CH-sepharose 4B, and Epoxy activated sepharose 6B. 3H-labeled heparin was used to check its binding capacity to sepharose gels. Binding of heparin to gel surface was found to be tight in AH-sepharose 4B, CH-sepharose 4B, and Epoxy activated sepharose 6B because of the difference of the binding sites of heparin free radicals but their recovery and purity of AT-III were poor.According to this experimental results, CNBr activated sepharose 4B was used for the purification of rat tissue AT-III and the metabolism of AT-III was investigated from the stand point of 14C-glycine. incorporation into AT-III fractions. 14C radioactivity in the tissue AT-III fractions were observed immediately after injection and reached to the maximum at 6 hours and appeared to be released into circulating pool in 2 hours after injection.

scholarly journals Calmodulin confers calcium sensitivity on ciliary dynein ATPase.

1980 ◽  
Vol 87 (2) ◽  
pp. 386-397 ◽  
Author(s):  
J J Blum ◽  
A Hayes ◽  
G A Jamieson ◽  
T C Vanaman
Keyword(s):  
Molecular Weight ◽  
Atpase Activity ◽  
High Molecular Weight ◽  
Binding Sites ◽  
Calcium Sensitivity ◽  
Bovine Brain ◽  
Calmodulin Binding ◽  
Dependent Atpase ◽  
Low Concentrations ◽  
Sepharose 4B

Extraction of demembranated cilia of Tetrahymena by Tris-EDTA (denoted by the suffix E) yields 14S-E and 30S-E dyneins with ATPase activities that are slightly increased by Ca++. This effect is moderately potentiated when bovine brain calmodulin is added to the assay mixture. Extraction with 0.5 M KCl (denoted by the suffix K) yeilds a 14S-K dynein with a low basal ATPase activity in the presence of Ca++. Subsequent addition of calmodulin causes marked activation (up to 10-fold) of ATPase activity. Although 14S-K and 14S-E dyneins have Ca++-dependent ATPase activities that differ markedly in the degree of activation, the concentration of calmodulin required for half-maximal saturation is similar for both, approximately 0.1 microM. Both 30S-K and 30S-E dyneins, however, require approximately 0.7 microM bovine brain calmodulin to reach half-maximal activation of their Ca++-dependent ATPase activities. Tetrahymena calmodulin is as effective as bovine brain calmodulin in activating 30S dynein , but may be slightly less effective than the brain calmodulin in activating 14S dynein. Rabbit skeletal muscle troponin C also activates the Ca++-dependent ATPase activity of 30S dynein and, to a lesser extent, that of 14S dynein, but in both cases is less effective than calmodulin. The interaction of calmodulin with dynein that results in ATPase activation is largely complete in less than 1 min, and is prevented by the presence of low concentrations of ATP. Adenylyl imidodiphosphate can partially prevent activation of dynein ATPase by calmodulin plus Ca++, but at much higher concentrations than required for prevention by ATP. beta, gamma-methyl-adenosine triphosphate appears not to prevent this activation. The presence of Ca++-dependent calmodulin-binding sites on 14S and 30S dyneins was demonstrated by the Ca++-dependent retention of the dyneins on a calmodulin-Sepharose-4B column. Gel electrophoresis of 14S dynein that had been purified by the affinity-chromatography procedure showed that presence of two major and one minor high molecular weight components. Similar analysis of 30S dynein purified by this procedure also revealed on major and one minor high molecular weight components that were different from the major components of 14S dynein. Ca++-dependent binding sites for calmodulin were shown to be present on axonemes that had been extracted twice with Tris-EDTA or with 0.5 M KCl by the use of 35S-labeled Tetrahymena calmodulin. It is concluded that the 14S and 30S dyneins of Tetrahymena contain Ca++-dependent binding sites for calmodulin and the calmodulin mediates the Ca++-regulation of the dynein ATPases of Tetrahymena cilia.

scholarly journals The effect of N-bromosuccinimide on the sub-unit structure of avidin and its complexes with biotin

1968 ◽  
Vol 110 (1) ◽  
pp. 59-66 ◽  
Author(s):  
N. M. Green ◽  
M. E. Ross
Keyword(s):  
Binding Sites ◽  
Oxidation Products ◽  
Guanidinium Chloride ◽  
Unit Structure ◽  
Tryptophan Residues ◽  
Biotin Binding ◽  
Tetrameric Complex ◽  
Chloride Concentrations ◽  
Avidin Biotin Complex

1. Each molecule of biotin bound to avidin protected four tryptophan residues from oxidation by N-bromosuccinimide, regardless of the occupancy of neighbouring binding sites in the four-sub-unit avidin molecule. 2. The oxidation products from avidin molecules in which some of the sites were occupied were separated on columns of Sephadex G-100. In the absence of biotin, oxidized avidin broke down into sub-units, which partly aggregated. When some of the sites were occupied by biotin, the only detectable products were completely oxidized avidin (sub-units and large aggregates) and unoxidized avidin–biotin complex (tetramer). Since the biotin-containing sub-units were randomly distributed before oxidation took place, they must have dissociated from the molecules containing oxidized sub-units and then reassociated to form the tetrameric avidin–biotin complex. 3. This reassociation still occurred in 3·5m-guanidinium chloride, which prevents the reassociation of unoccupied sub-units. During their brief existence in this medium, the sub-units of avidin–biotin complex were protected from oxidation by N-bromo-succinimide to the same extent as was the tetrameric complex. 4. It is concluded that sub-units of avidin–biotin complex do not readily lose their biotin, even in 3·5m-guanidinium chloride, and that monomeric biotin–binding species are probably present in solutions of avidin sub-units at guanidinium chloride concentrations between 3·0m and 3·5m.

scholarly journals Purification and characterization of CS2, a sialic acid-specific haemagglutinin of enterotoxigenic Escherichia coli

1988 ◽  
Vol 255 (1) ◽  
pp. 105-111 ◽  
Author(s):  
P O Sjöberg ◽  
M Lindahl ◽  
J Porath ◽  
T Wadström
Keyword(s):  
Escherichia Coli ◽  
Sialic Acid ◽  
Gel Filtration ◽  
Enterotoxigenic Escherichia Coli ◽  
Guanidinium Chloride ◽  
Neuraminidase Treatment ◽  
Low Concentrations ◽  
Sepharose 4B ◽  
Bovine Erythrocytes

CS2 fimbriae of enterotoxigenic Escherichia coli were purified and characterized. The surface haemagglutinins (fimbriae) were detached by sonication from a strain producing only the CS2 fimbriae. Isolation was carried out by gel filtration on a Sepharose 4B column. After depolymerization, the fimbriae subunits were purified on a Sephacryl S-300 column in 8.0 M-guanidinium chloride. From 1 litre of medium, 4-6 mg of purified fimbriae was obtained. We found that CS2 fimbriae were completely dissociated by saturated guanidinium chloride into subunits with a molecular mass of 16.5 kDa. CS2 fimbriae was sialic acid-specific, since sialic acids were the most potent inhibitors, and neuraminidase treatment of erythrocytes abolished haemagglutination. Both fimbriae and fimbrial subunits were found to bind to bovine erythrocytes. The binding of subunits to erythrocytes could be inhibited with low concentrations of sialyl-lactose.

Colchicine Uptake and Binding by Human Platelets

1975 ◽  
Vol 34 (03) ◽  
pp. 780-794 ◽  
Author(s):  
Dianne M Kenney ◽  
Francis C Chao ◽  
James L Tullis ◽  
Gail S Conneely
Keyword(s):  
Time Dependence ◽  
Incubation Period ◽  
Binding Sites ◽  
Silicone Oil ◽  
Cold Treatment ◽  
Human Platelets ◽  
Temperature Dependent

SummaryThe uptake and binding of antimitotic alkaloid colchicine has been demonstrated in washed preparations of human platelets. A silicone oil technique was adapted so that both uptake and binding of 14C-colchicine were examined in the same platelet preparations. The time dependence and amount of colchicine taken up and bound by different platelet preparations during a 90 to 120 min incubation period were highly reproducible. Both colchicine uptake and binding by intact platelets, and colchicine binding by preparations of lysed platelets were specific and temperature dependent. Colchicine uptake was slowly reversible. Magnesium and GTP enhanced colchicine binding by lysed platelet preparations but calcium decreased binding.Exposure of platelets to either cold (4° C) or to thrombin, which disrupt platelet microtubules, produced significant increases in colchicine uptake and binding. The thrombin effect was maximal at 37° C and resulted in a greater increase in uptake and binding than that produced by either cold treatment alone or, by cold treatment followed by incubation with thrombin at 37° C. The amount of increase in uptake and binding produced by thrombin was independent of both thrombin (1–5 Units/109 platelets) and colchicine concentrations (1–50 × 10−6M).It is postulated that thrombin may initiate the formation, or make available, colchicine binding sites (microtubule subunits) within platelets.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

scholarly journals Structures of the somatotropin receptor and prolactin receptor on rat hepatocytes characterized by affinity labelling

1984 ◽  
Vol 220 (2) ◽  
pp. 361-369 ◽  
Author(s):  
K Yamada ◽  
D B Donner
Keyword(s):  
Binding Sites ◽  
Prolactin Receptor ◽  
Rat Hepatocytes ◽  
Membrane Receptors ◽  
Bovine Somatotropin ◽  
Male Rats ◽  
Disulphide Bonds ◽  
Low Concentrations ◽  
Affinity Labelling ◽  
Structural Descriptions

Human somatotropin competed for 125I-human somatotropin binding to hepatocytes from female or male rats. Bovine somatotropin and prolactin each inhibited part, but not all, of the uptake of 125I-human somatotropin. The binding of 125I-prolactin was inhibited by human somatotropin and prolactin, but not by bovine somatotropin. Bovine somatotropin and human somatotropin, but not prolactin, competed for 125I-bovine somatotropin binding sites. 125I-labelled hormones were covalently coupled to membrane receptors with higher efficiency on hepatocytes from female than from male rats, allowing structural descriptions of lactogenic and somatogenic binding sites that had not been possible previously. Disuccinimidyl suberate covalently coupled 125I-human somatotropin into saturable complexes of Mr 300 000, 220 000, 130 000, 65 000 and 50 000. Bovine somatotropin inhibited the incorporation of 125I-human somatotropin into complexes of Mr 300 000, 220 000 and 130 000, whereas low concentrations of prolactin competed for incorporation into the 65 000- and 50 000-Mr species. 125I-bovine somatotropin was incorporated into complexes of Mr 300 000, 220 000 and 130 000. Human somatotropin and bovine somatotropin, but not prolactin, inhibited the production of these complexes. 125I-prolactin binding produced complexes of Mr 65 000 and 50 000. Native prolactin and human somatotropin, but not bovine somatotropin, inhibited uptake of 125I-prolactin into these species. Thus direct affinity labelling, as well as competition for covalent coupling, suggests that the 300 000-, 220 000- and 130 000-Mr species are components of the somatotropin receptor and that the 65 000- and 50 000-Mr complexes result from hormone binding to the prolactin receptor. By subtracting the Mr of prolactin, it was calculated that the hormone was bound to species of Mr 43 000 and 28 000. These Mr values were not affected by reduction of solubilized membranes, suggesting that the structure of the prolactin receptor is not stabilized by interchain disulphide bonds between subunits. Subtracting the Mr of somatotropin from somatogenic complexes indicated that the hormone had bound to species of Mr 280 000, 200 000 and 100 000. The 300 000- and 220 000-Mr complexes were not isolated from reduced membranes, whereas the amount of the 130 000-Mr species was augmented. These observations could suggest that a major component of the somatotropin receptor is a trimeric aggregate in which some subunits are retained in a larger complex by interchain disulphide bonds.

Specific binding sites for ovine prolactin in three amphibian cell lines

1985 ◽  
Vol 248 (1) ◽  
pp. C80-C87 ◽  
Author(s):  
M. Dunand ◽  
M. L. Aubert ◽  
J. P. Kraehenbuhl ◽  
B. C. Rossier
Keyword(s):  
Growth Hormone ◽  
Cell Lines ◽  
Binding Sites ◽  
Binding Capacity ◽  
Specific Binding ◽  
Human Growth ◽  
Functional Differentiation ◽  
Water Metabolism ◽  
Ovine Prolactin ◽  
Follicle Stimulating Hormones

Established cell lines (TB-6c and TB-M) obtained by continuous culture of epithelial cells from toad Bufo marinus urinary bladder, which, in culture, maintained a high degree of functional differentiation, exhibited a significant number of high-affinity (KA = 1-2 X 10(10) M-1) binding sites detected both with radioiodinated (125I) ovine prolactin (oPRL) and human growth hormone (hGH). Binding capacity was higher in the case of TB-6c cells (7,573 +/- 581 sites/cell) than with the TB-M cells (1,160 +/- 87). Similarly, binding sites for oPRL were characterized on Xenopus laevis kidney-derived cell line A6. With oPRL used both as tracer and standard, significant cross-reaction was observed with hGH, less with human or rat prolactin (PRL), and none with human chorionic somatomammotropin, bovine growth hormone, and rat luteinizing hormone or follicle-stimulating hormones. B. marinus pituitary extracts completely displaced the binding of 125I-oPRL to toad bladder binding sites. This finding of specific sites for PRL on amphibian bladder and kidney cells confirms that PRL exerts specific biological actions for the control of electrolyte and water metabolism in the amphibians.

scholarly journals Cortical RORβ is required for layer 4 transcriptional identity and barrel integrity

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Erin A Clark ◽  
Michael Rutlin ◽  
Lucia Capano ◽  
Samuel Aviles ◽  
Jordan R Saadon ◽  
...  
Keyword(s):  
Binding Sites ◽  
Binding Capacity ◽  
Chromatin Accessibility ◽  
Excitatory Input ◽  
Orphan Receptor ◽  
Knock Out ◽  
Putative Target ◽  
Layer 4 ◽  
The Relationship ◽  
Receptor Beta

Retinoic acid-related orphan receptor beta (RORβ) is a transcription factor (TF) and marker of layer 4 (L4) neurons, which are distinctive both in transcriptional identity and the ability to form aggregates such as barrels in rodent somatosensory cortex. However, the relationship between transcriptional identity and L4 cytoarchitecture is largely unknown. We find RORβ is required in the cortex for L4 aggregation into barrels and thalamocortical afferent (TCA) segregation. Interestingly, barrel organization also degrades with age in wildtype mice. Loss of RORβ delays excitatory input and disrupts gene expression and chromatin accessibility, with down-regulation of L4 and up-regulation of L5 genes, suggesting a disruption in cellular specification. Expression and binding site accessibility change for many other TFs, including closure of neurodevelopmental TF binding sites and increased expression and binding capacity of activity-regulated TFs. Lastly, a putative target of RORβ, Thsd7a, is down-regulated without RORβ, and Thsd7a knock-out alone disrupts TCA organization in adult barrels.

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