scholarly journals Changing pattern of cyclic AMP-binding proteins during germination of Mucor racemosus sporangiospores

1979 ◽  
Vol 182 (2) ◽  
pp. 547-554 ◽  
Author(s):  
M Orlowski
Keyword(s):  
Cyclic Amp ◽  
Time Course ◽  
Binding Proteins ◽  
Dissociation Constants ◽  
Binding Capacity ◽  
Specific Binding ◽  
Polyacrylamide Gel Electrophoresis ◽  
Mucor Racemosus ◽  
Response Curves ◽  
Kd Values

Interation of cyclic AMP with a profoundly changing pattern of specific binding proteins was shown during aerobic germination of sporangiospores from the fungus Mucor racemosus. 32P-labeled 8-azido-cycli AMP, an analogue of cyclic AMP that forms a covalent linkage with the binding proteins under u.v. light, was used as the ligand. Binding proteins carrying this photoaffinity label were separated by polyacrylamide-gel electrophoresis and identified by radioautography. Equibiltrium dissociation constants (Kd) and binding-response curves in the presence of competing nucleotides were identical for both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP. A quantitative binding assay with both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP over the time course of sporangiospore germination indicated a parallel relationship between cyclic AMP-binding capacity and the intracellular concentrations of cyclic AMP reported in a previous study [Paznokas & Sypherd (1975) J. Bacteriol. 124, 134–139]. Both of these parameters attained transient high values at a time of development when addition of exogenous cyclic AMP prevents hyphal-germ-tube emergence. The measured Kd values did not change during sport germination.

Characterization of galanin receptor in canine small intestinal circular muscle synaptosomes

1994 ◽  
Vol 266 (1) ◽  
pp. G106-G112 ◽  
Author(s):  
C. K. Chen ◽  
T. J. McDonald ◽  
E. E. Daniel
Keyword(s):  
Small Intestine ◽  
Binding Site ◽  
G Protein ◽  
Binding Capacity ◽  
Specific Binding ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Circular Muscle ◽  
Galanin Receptor ◽  
High Affinity

We used 125I-galanin (porcine) as ligand to study the galanin receptors in circular muscle and deep muscular plexus from canine small intestine. Specific binding sites were found in both nerve and muscle membranes. On synaptosomal membranes, the equilibrium binding study showed a high-affinity (dissociation constant, Kd = 1.1 +/- 0.13 nM; maximum binding capacity, Bmax = 244 +/- 2.1 fmol/mg) binding site. The specific binding of 125I-galanin to nerve membrane was inhibited by galanin or NH2-terminal galanin fragments but not by the COOH-terminal fragment. Computer analysis suggested a two-site model (inhibitor constants, Ki1 = 0.02 +/- 0.005 nM and Ki2 = 1.05 +/- 0.3 nM) for competition by galanin-(1-29). Kinetic and competition studies using guanosine 5'-O-(3-thiotriphosphate) or pertussis toxin (PTX) suggested that the high-affinity binding site involved a PTX-sensitive G protein which acted to slow dissociation of bound galanin from the receptor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the galanin receptor complex revealed a radioactive band at 50 kDa. We conclude that, in canine small intestine, galanin may act as an inhibitory neuromodulator by a PTX-sensitive G protein-coupled interaction of galanin and its specific receptor on enteric nerve synaptosomes

Characterization of vasopressin receptors of rat urinary bladder and spleen

1986 ◽  
Vol 251 (1) ◽  
pp. H115-H120 ◽  
Author(s):  
M. Thibonnier ◽  
R. M. Snajdar ◽  
J. P. Rapp
Keyword(s):  
Urinary Bladder ◽  
Cyclic Amp ◽  
Binding Sites ◽  
Binding Capacity ◽  
Specific Binding ◽  
Experimental Hypertension ◽  
Sprague Dawley ◽  
Rat Urinary Bladder ◽  
Vascular Type ◽  
Vasopressin Receptors

By use of tritiated arginine-8-vasopressin (AVP), vasopressin specific binding sites were detected on Sprague-Dawley rat urinary bladder and spleen. In both tissues, one class of high-affinity binding sites was characterized with an equilibrium dissociation constant of 1.61 +/- 0.22 and 1.91 +/- 0.16 nM and a maximal binding capacity of 155 +/- 5 and 110 +/- 11 fmol/mg of protein, for bladder and spleen, respectively. In both tissues, several experimental arguments suggest that these receptors belong to the V1-vascular type: Highly significant correlations were found between the relative agonistic vasopressor activities of eight AVP agonists and their relative abilities to inhibit [3H]AVP binding to the receptors, whereas no such relationship existed when antidiuretic activities were considered. The same profile was also observed with the antagonistic activities of five AVP antagonists. Moreover, AVP (10(-12)-10(-5) M) did not modify the basal cyclic AMP production in either tissue. As cyclic AMP is known to respond to V2 stimulation, the data suggest that the receptors measured are the V1 type. In Dahl rats the receptor characteristics were modulated by salt diet. More interestingly, the number of spleen vasopressin binding sites was always lower in Dahl salt-resistant animals than in the Dahl salt-sensitive animals receiving either a sodium deficient or a 1% NaCl or an 8% NaCl-containing diet. The exploration of vasopressin receptors regulation should facilitate the comprehension of the role played by AVP in different models of experimental hypertension.

scholarly journals Human platelets are defective in processing of cholera toxin

1983 ◽  
Vol 212 (3) ◽  
pp. 669-678 ◽  
Author(s):  
R J Hughes ◽  
P A Insel
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Mammalian Cells ◽  
Time Course ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Human Platelets ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity

Cholera toxin is unable to elevate cyclic AMP levels in intact human platelets despite being very efficacious in this respect in other mammalian cells; in the presence of 0.5 mM-isobutylmethylxanthine, we found that 3-6nM-cholera toxin over 3h at 37 degrees C elevated platelet cyclic AMP from 33 +/- 13 to 39 +/- 12pmol/mg of protein (means +/- S.D.; n = 12). We have investigated the basis for this lack of response. 125I-labelled cholera toxin bound to platelets both saturably and with high affinity (Kd congruent to 60pM; Bmax. congruent to 50fmol/mg of protein). Incubation of platelets with the putative cholera toxin receptor monosialoganglioside GM1 enhanced 125I-labelled cholera toxin binding at least 40-fold but facilitated only a minimal (less than or equal to 3-fold) elevation of platelet cyclic AMP levels. In contrast, dithiothreitol-activated cholera toxin markedly stimulated adenylate cyclase activity in platelet membranes. Platelet cytosol both enhanced stimulation of adenylate cyclase activity by activated cholera toxin (A1 subunit) and supported stimulation by the A1-A2 subunit of cholera toxin. Neither GTP nor NAD+, both necessary for response to cholera toxin, was lacking in intact platelets. However, we found that platelets were unable to cleave cholera toxin to the active A1 subunit (as assessed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis). By contrast, murine S49 lymphoma cells were able to generate the A1 subunit with a time course that closely resembled the kinetics of toxin-mediated cyclic AMP accumulation in these cells. Thus we conclude that human platelets are defective in their ability to process surface-bound cholera toxin. These results indicate that binding of cholera toxin to surface receptors is necessary, but not sufficient, for expression of the toxin effect and the generation of the A1 subunit of the toxin may be rate-limiting for expression of cholera toxin response.

THE THYROXINE-BINDING PROPERTIES OF SERUM PROTEINS. A COMPETITIVE BINDING TECHNIQUE EMPLOYING SEPHADEX G-25

1975 ◽  
Vol 65 (3) ◽  
pp. 319-332 ◽  
Author(s):  
R. L. SUTHERLAND ◽  
M. W. SIMPSON-MORGAN
Keyword(s):  
Binding Proteins ◽  
Serum Proteins ◽  
Binding Capacity ◽  
Specific Binding ◽  
Competitive Binding ◽  
Association Constants ◽  
Binding Properties ◽  
Rat Serum ◽  
Human Proteins ◽  
Dilute Blood

SUMMARY A competitive binding technique is described for the estimation of the thyroxine (T4)-binding properties of serum proteins in dilute blood serum and lymph. When used in conjunction with an assay for total T4 the following parameters can be estimated: the number of functionally different T4 binding proteins, their individual association constants and binding capacities for T4, the amount of T4 which is bound to each binding species, and the concentration of unbound (free) T4. Both human and sheep serum have three functionally different T4-binding proteins. The association constants for the three human proteins were 9·5 × 109, 1·6 × 108 and 3·1 × 105 1/mol for T4-binding globulin (TBG), T4-binding prealbumin (TBPA) and serum albumin, respectively. The corresponding sheep proteins, TBG, TBP-2 and albumin, had association constants of 8·9 × 109, 1·4 × 108 and 3·5 × 1051/mol. Human TBG had a mean binding capacity of 21·3 μg/100 ml and that of ovine TBG was 12·8 μg/100 ml. The other specific binding proteins (TBPA in man and TBP-2 in sheep) had mean binding capacities of 307 and 359 μg/100 ml respectively. Two functionally different T4-binding proteins were identified in rat serum.

Interaction of vasoactive intestinal peptide with rat small intestinal epithelial cells after intestinal resection

1985 ◽  
Vol 5 (7) ◽  
pp. 559-566 ◽  
Author(s):  
José L. Diaz-Juarez ◽  
Guillermo Bodega ◽  
Eduardo Arilla ◽  
Juan C. Prieto
Keyword(s):  
Epithelial Cells ◽  
Cyclic Amp ◽  
Vasoactive Intestinal Peptide ◽  
Intestinal Epithelial Cells ◽  
Binding Capacity ◽  
Specific Binding ◽  
Intestinal Resection ◽  
Intestinal Epithelial ◽  
Cyclic Amp Accumulation ◽  
Small Intestinal

Specific binding of vasoactive intestinal peptide (VIP) and VIP-stimulated cyclic AMP accumulation were studied in small intestinal epithelial cells (both of crypt and villous levels) 3, 7 and 14 d after a 60% resection of the small intestine. The affinity, but not the binding capacity, of VIP receptors decreased during the adaptive hyperplastic response. Basal cyclic AMP levels were similar in cells of both control and resected rats. Resection induced a decrease of potency, but not of efficiency, of VIP on the stimulation of cyclic AMP accumulation.

scholarly journals Cyclic AMP-binding and cyclic AMP-dependent protein kinase activities in the cytosol of differentiating bone marrow erythroblasts

1981 ◽  
Vol 196 (3) ◽  
pp. 893-897 ◽  
Author(s):  
M S Setchenska ◽  
J G Vassileva-Popova ◽  
H R Arnstein
Keyword(s):  
Bone Marrow ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Binding Proteins ◽  
Kinase Activity ◽  
Binding Capacity ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Dividing Cells ◽  
Dependent Protein

Cytosolic cyclic AMP-binding capacity and cyclic AMP-dependent protein kinase activity have been studied in relation to differentiation and maturation of rabbit bone marrow erythroblasts. Using cells fractionated by velocity sedimentation at unit gravity, it was found that both activities decreased in dividing cells when calculated in terms of cell number but remained constant per cell volume. After the final cell division, cyclic AMP-dependent protein kinase activity did not change further, whereas cyclic AMP-binding capacity declined. There were no qualitative, but only quantitative, changes in the cyclic AMP-binding proteins that are present in the cytosol of developing erythroblasts. In the immature cells, the apparent KD for the interaction of binding proteins with cyclic AMP was 4 } 10(-8) M. The data suggest that changes in cyclic AMP-binding activity during differentiation of erythroid cells are due both to changes in the amount of binding proteins and in their affinity for cyclic AMP. Plasma membranes of erythroblasts were also able to bind cyclic AMP but only in dividing cells.

Identification of a set of calcium-binding proteins in reticuloplasm, the luminal content of the endoplasmic reticulum

1988 ◽  
Vol 91 (1) ◽  
pp. 61-70 ◽  
Author(s):  
D.R. Macer ◽  
G.L. Koch
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Binding ◽  
Binding Proteins ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Calcium Ionophore ◽  
Binding Activity ◽  
Calcium Binding Proteins ◽  
Molecular Weights

A procedure was developed for the isolation of reticuloplasm, the luminal material of the endoplasmic reticulum (ER). A reticuloplasm-rich extract was prepared from a murine plasmacytoma cell line that contains large amounts of ER, by first extracting the cytoplasmic contents using hypotonic lysis to yield ER-rich ‘shells’ followed by mechanical lysis to release the ER contents. The extract contains five major proteins with apparent molecular weights of 100, 75, 60, 58 and 55 (X 10(3] Mr by SDS-polyacrylamide gel electrophoresis. The 100, 75 and 58 (X 10(3] Mr species were identified as the known ER proteins endoplasmin, BiP and PD1, respectively. The ER association of the 60 and 55 (X 10(3] Mr proteins was confirmed by confocal fluorescence microscopy with affinity-purified antibodies. Equilibrium dialysis with isolated reticuloplasm gave a calcium-binding capacity of 300 nmoles calcium per mg protein with half-maximal binding at 3 mM-Ca2+. Purified endoplasmin bound 280 nmoles calcium per mg protein at a calcium concentration of 5 mM-Ca2+. A calcium overlay test revealed that, in addition to endoplasmin, reticuloplasm contained at least three other calcium-binding proteins: i.e. BiP, PDI and the 55 X 10(3) Mr protein, respectively, with endoplasmin and the 55 X 10(3) Mr protein (CRP55) accounting for the major proportion of the calcium-binding activity. Treatment of cells with calcium ionophore led to the specific over-expression of the major calcium-binding reticuloplasmins endoplasmin, BiP and CRP55. These studies show that the lumen of the ER contains a family of proteins with the capacity to bind significant amounts of calcium in the millimolar range and thereby to confer upon the ER the ability to perform a calcium storage function analogous to that of the sarcoplasmic reticulum in muscle cells.

scholarly journals Simulation/Experiment Confrontation, an Efficient Approach for Sensitive SAW Sensors Design

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4994
Author(s):  
Bilel Achour ◽  
Ghada Attia ◽  
Chouki Zerrouki ◽  
Najla Fourati ◽  
Kosai Raoof ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Dissociation Constants ◽  
Limit Of Detection ◽  
Fem Simulation ◽  
Response Curves ◽  
Time Saving ◽  
Fourfold Increase ◽  
Sensing Applications ◽  
Kd Values ◽  
Good Agreement

Sensitivity is one of the most important parameters to put in the foreground in all sensing applications. Its increase is therefore an ongoing challenge, particularly for surface acoustic wave (SAW) sensors. Herein, finite element method (FEM) simulation using COMSOL Multiphysics software is first used to simulate the physical and electrical properties of SAW delay line. Results indicate that 2D configuration permits to accurately obtain all pertinent parameters, as in 3D simulation, with very substantial time saving. A good agreement between calculation and experiment, in terms of transfer functions (S21 spectra), was also shown to evaluate the dependence of the SAW sensors sensitivity on the operating frequency; 2D simulations have been conducted on 104 MHz and 208 MHz delay lines, coated with a polyisobutylene (PIB) as sensitive layer to dichloromethane (DCM). A fourfold increase in sensitivity was obtained by doubling frequency. Both sensors were then realized and tested as chem-sensors to detect zinc ions in liquid media. 9-{[4-({[4-(9anthrylmethoxy)phenyl]sulfanyl} methyl)]methyl] anthracene (TDP-AN) was selected as the sensing layer. Results show a comparable response curves for both designed sensors, in terms of limit of detection and dissociation constants Kd values. On the other hand, experimental sensitivity values were of the order of [7.0 ± 2.8] × 108 [°/M] and [16.0 ± 7.6] × 108 [°/M] for 104 MHz and 208 MHz sensors, respectively, confirming that the sensitivity increases with frequency.

Studies on Z-Fraction. I. Isolation and Partial Characterization of Low Molecular Weight Ligand-Binding Protein from Rat Hepatic Cytosol

1975 ◽  
Vol 53 (3) ◽  
pp. 493-500 ◽  
Author(s):  
Margaret Warner ◽  
Allen H. Neims
Keyword(s):  
Molecular Weight ◽  
Ligand Binding ◽  
Dissociation Constants ◽  
Binding Capacity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Partial Characterization ◽  
Fraction I ◽  
Z Protein

The Z-fraction has been defined operationally as a ligand-binding (bilirubin sulfobromophthalein) portion of rat hepatic cytosol that elutes in the molecular weight region of 104 daltons after gel filtration. Polyacrylamide gel electrophoreses under different conditions, as well as binding stoichiometry, confirm the anticipated heterogeneity of the Z-fraction. Three factors have contributed to the subsequent resolution of the Z-fraction and partial characterization of that protein within the fraction with ligand-binding properties (Z-protein): (1) the use of hexachlorophene as ligand; (2) the inclusion of glycerol, 20%, during isolation to prevent aggregation and loss of binding-activity; and (3) the development of a charcoal binding assay. Upon ion exchange chromatography, the Z-fraction resolves into a group of distinct protein components and an unidentified material with a high 260/280 nm absorbancy ratio. The one protein component with binding capacity exhibits homogeneity on polyacrylamide gel electrophoresis (11% gel, Ann. N.Y. Acad. Sci. 121, 404–427, 1964; and 15% gel with SDS). With use of the charcoal method, apparent dissociation constants for the interaction between Z-protein and hexachlorophene, bilirubin and L-thyroxine, were found to be 20, 50, and 350 μM, respectively. The Scatchard plot generated upon extrapolation an n value of 1.0 with assumption of a molecular weight for Z-protein of 104 daltons.

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