scholarly journals Direct in vivo demonstration by radioautography of specific binding sites for calcitonin in skeletal and renal tissues of the rat.

1980 ◽  
Vol 85 (3) ◽  
pp. 682-694 ◽  
Author(s):  
H Warshawsky ◽  
D Goltzman ◽  
M F Rouleau ◽  
J J Bergeron
Keyword(s):  
Binding Sites ◽  
Alveolar Bone ◽  
Specific Binding ◽  
Biologically Active ◽  
Target Cells ◽  
Rat Tissues ◽  
Specific Binding Sites ◽  
Calcitonin Receptors

An in vivo binding assay using radioautography was employed to visualize calcitonin receptors in rat tissues. At 2 min after intravenous injection of biologically active 125I-salmon calcitonin, free hormone was separated from bound hormone by intracardiac perfusion with lactated Ringer's followed by fixation with 2.5% glutaraldehyde. Various tissues were removed and processed for light and electron microscope radioautography. These were compared to tissues removed from animals that received identical amounts of labeled hormone with a large excess of unlabeled calcitonin. Among the tissues investigated, kidney and bone demonstrated labeling. In kidney, most silver grains were located over vesicles below the brush border of cells of theproximal convoluted tubules. These grains were still present after simultaneous injection of excess unlabeled hormone and most likely represented binding to sites involved with ingestion and degradation of hormone from the urinary filtrate. In contrast, grains localized to the basal surfaces of distal convoluted tubule cells were significantly reduced in number in control animals and represented sites of saturable, specific hormone binding. In bone, specific binding sites were found only at the periphery of osteoclasts. These labeled cells were located at resorption sites examined in tibia, humerus, and alveolar bone. This demonstration of the localization of 124I-calcitonin in situ provides a new approach for study the interaction of calcium-regulating hormones with their target cells.

Atrial natriuretic factor binding sites in the jejunum

1989 ◽  
Vol 256 (2) ◽  
pp. G436-G441 ◽  
Author(s):  
C. Bianchi ◽  
G. Thibault ◽  
A. De Lean ◽  
J. Genest ◽  
M. Cantin
Keyword(s):  
Binding Sites ◽  
Atrial Natriuretic Factor ◽  
Specific Binding ◽  
Rat Tissues ◽  
Rat Jejunum ◽  
Specific Binding Sites ◽  
Natriuretic Factor ◽  
Atrial Natriuretic

We have studied the localization and the characterization of atrial natriuretic factor (ANF) binding sites by radioautographic techniques. Quantitative in vitro radioautography with a computerized microdensitometer demonstrated the presence of high-affinity, low-capacity 125I-ANF-(99-126) binding sites (Kd, 48 pM; Bmax, 63 fmol/mg protein) mainly in the villi of 20-microns slide-mounted transverse sections of the rat jejunum. Competition curves showed 50% inhibitory concentrations of 55 and 1,560 pM for ANF-(99-126) and ANF-(103-123), respectively. In vivo electron microscope radioautography showed that 80% of the silver grains were localized on the lamina propria fibroblast-like cells, 18% on mature enterocytes, and 2% on capillaries. Bradykinin and adrenocorticotropin did not compete with ANF binding. These results demonstrate that ANF binding sites in the rat jejunum possess the pharmacological characteristics of functional ANF receptors encountered in other rat tissues, and ultrastructural radioautographs show their cellular distribution. Taken together, these results demonstrate the presence and the localization of specific binding sites for ANF in the jejunal villi of the rat small intestine.

scholarly journals A quantitative binding model for the Apl protein, the dual purpose recombination-directionality factor and lysis-lysogeny regulator of bacteriophage 186

2020 ◽  
Vol 48 (16) ◽  
pp. 8914-8926
Author(s):  
Erin E Cutts ◽  
J Barry Egan ◽  
Ian B Dodd ◽  
Keith E Shearwin
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Attachment Site ◽  
Binding Energies ◽  
Sequence Specificity ◽  
Binding Studies ◽  
Binding Model ◽  
Specific Binding Sites

Abstract The Apl protein of bacteriophage 186 functions both as an excisionase and as a transcriptional regulator; binding to the phage attachment site (att), and also between the major early phage promoters (pR-pL). Like other recombination directionality factors (RDFs), Apl binding sites are direct repeats spaced one DNA helix turn apart. Here, we use in vitro binding studies with purified Apl and pR-pL DNA to show that Apl binds to multiple sites with high cooperativity, bends the DNA and spreads from specific binding sites into adjacent non-specific DNA; features that are shared with other RDFs. By analysing Apl's repression of pR and pL, and the effect of operator mutants in vivo with a simple mathematical model, we were able to extract estimates of binding energies for single specific and non-specific sites and for Apl cooperativity, revealing that Apl monomers bind to DNA with low sequence specificity but with strong cooperativity between immediate neighbours. This model fit was then independently validated with in vitro data. The model we employed here is a simple but powerful tool that enabled better understanding of the balance between binding affinity and cooperativity required for RDF function. A modelling approach such as this is broadly applicable to other systems.

scholarly journals Theory of site-specific DNA-protein interactions in the presence of nucleosome roadblocks

2017 ◽  
Author(s):  
R. Murugan
Keyword(s):  
Protein Interactions ◽  
Binding Sites ◽  
Specific Binding ◽  
First Passage Time ◽  
Free Energy Barrier ◽  
Site Specific ◽  
Specific Binding Sites ◽  
Genome Wide ◽  
Diffusion Dynamics

AbstractWe show that nucleosomes can efficiently control the relative search times spent by transcription factors (TFs) on one- (1D) and three-dimensional (3D) diffusion routes towards locating their cognate sites on DNA. Our theoretical results suggest that the roadblock effects of nucleosomes are dependent on the relative position on DNA with respect to TFs and their cognate sites. Especially, nucleosomes exert maximum amount of hindrance to the 1D diffusion dynamics of TFs when they are positioned in between TFs and their cognate sites. The effective 1D diffusion coefficient (χTF) associated with the dynamics of TFs in the presence of nucleosome decreases with the free energy barrier (µ) associated the sliding dynamics of nucleosomes as . Subsequently the mean first passage time (ηL) that is required by TFs to scan L number of binding sites on DNA via 1D diffusion increases with μ as . When TFs move close to nucleosomes then they exhibit a typical sub-diffusive dynamics. Nucleosomes can enhance the search dynamics of TFs when TFs present in between nucleosomes and transcription factor binding sites (TFBS). The level of enhancement effects of nucleosomes seems to be much lesser than the level of retardation effects when nucleosomes present in between TFs and their cognate sites. These results suggest that nucleosome depleted regions around the cognate sites of TFs is mandatory for an efficient site-specific interactions of TFs with DNA. Remarkably the genome wide positioning pattern of TFs shows maximum at their specific binding sites and the positioning pattern of nucleosome shows minimum at the specific binding sites of TFs under in vivo conditions. This seems to be a consequence of increasing level of breathing dynamics of nucleosome cores and decreasing levels of fluctuations in the DNA binding domains of TFs as they move across TFBS. Since the extent of breathing dynamics of nucleosomes and fluctuations in the DBDs of TFs are directly linked with their respective 1D diffusion coefficients, the dynamics of TFs becomes slow as they approach their cognate sites so that TFs form tight site-specific complex. Whereas the dynamics of nucleosomes becomes rapid so that they pass through the cognate sites of TFs. Several in vivo datasets on genome wide positioning pattern of nucleosomes as well as TFs seem to agree well with our arguments. We further show that the condensed conformational state of DNA can significantly decrease the retarding effects of nucleosome roadblocks. The retarding effects of nucleosomes on the 1D diffusion dynamics of TFs can be nullified when the degree of condensation of the genomic DNA is such that it can permit a jump size associated with the dynamics of TFs beyond k > 150 bps.

Targets for SMR1-pentapeptide suggest a link between the circulating peptide and mineral transport

1997 ◽  
Vol 273 (4) ◽  
pp. R1309-R1320 ◽  
Author(s):  
C. Rougeot ◽  
R. Vienet ◽  
A. Cardona ◽  
L. Le Doledec ◽  
J. M. Grognet ◽  
...  
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Basic Amino Acid ◽  
Whole Body ◽  
Male Rat ◽  
Amino Acid Residues ◽  
Dental Tissue ◽  
Specific Binding Sites ◽  
Mineral Transport

The submandibular rat 1 protein (SMR1) is selectively processed at pairs of basic amino acid residues in a tissue- and sex-specific manner. We have mapped peripheral targets for the final secretory maturation product of SMR1, the pentapeptide QHNPR, by examining in vivo the tissue distribution of the radiolabeled peptide using β-radio imager whole body autoradiography. The characteristics of tissue uptake allowed specific binding sites at physiological peptide concentrations to be identified within the renal outer medulla, bone and dental tissue, glandular gastric mucosa, and pancreatic lobules. Direct evidence that pentapeptide binding sites are localized in selective portions of the male rat nephron, within the S3, S2, and S1 segments of the proximal tubules, was obtained. In bone tissue the pentapeptide exclusively accumulates within the trabecular bone remodeling unit, and in dental tissue it concentrates within the tubules of the dentinal rat incisor. In relation to male rat-specific behavioral characteristics, our data suggest that the circulating androgen-regulated SMR1-derived pentapeptide is primarily involved in the modulation of mineral balance between at least four systems: kidney, bone, tooth, and circulation.

scholarly journals Contribution of gangliosides to thyroxin binding with plasma membranes

1995 ◽  
Vol 41 (2) ◽  
pp. 28-30
Author(s):  
T. S. Saatov ◽  
F. Ya. Gulyamova ◽  
G. U. Usmanova
Keyword(s):  
Binding Sites ◽  
Plasma Membranes ◽  
Binding Capacity ◽  
Specific Binding ◽  
Brain Cell ◽  
Cell Recognition ◽  
High Affinity ◽  
Specific Binding Sites

Besides intracellular receptors of thyroid hormones, specific binding sites for T3 and T4 were detected on plasma membranes (PM) of some cells and a relationship between membrane reception .and lipid composition of membranes shown. The parameters of 125I-T4 binding to highly purified PM of hepatic and cerebral cells of rats were studied. The hepatic and cerebral cellular membranes were found to contain two sites of hormone binding each, one of these sites being characterized by a high affinity and low capacity, and the other by low affinity and a higher binding capacity. The association constant of highly affine site of hepatocyte membranes was found to be higher than that of brain cell membranes. T4 membranous receptors may be significant in the process of cell “recognition" by the hormone. In vivo and in vitro experiments with 125I-T4 and 14C-labeled thyroxin in ganglioside fractions showed appreciable binding of the hormone to Gm3 fraction, this evidently pointing to participation of this, ganglioside in T4 interaction with membrane receptor. It is possible that gangliosides situated on membranous surface are components of or function as receptors.

scholarly journals Specific binding sites for albumin restricted to plasmalemmal vesicles of continuous capillary endothelium: receptor-mediated transcytosis.

1986 ◽  
Vol 102 (4) ◽  
pp. 1304-1311 ◽  
Author(s):  
L Ghitescu ◽  
A Fixman ◽  
M Simionescu ◽  
N Simionescu
Keyword(s):  
Plasma Membrane ◽  
Binding Sites ◽  
Specific Binding ◽  
Short Exposure ◽  
Gold Complex ◽  
Membrane Microdomains ◽  
Capillary Endothelium ◽  
Plasmalemmal Vesicles ◽  
Specific Binding Sites

The interaction of homologous and heterologous albumin-gold complex (Alb-Au) with capillary endothelium was investigated in the mouse lung, heart, and diaphragm. Perfusion of the tracer in situ for from 3 to 35 min was followed by washing with phosphate-buffered saline, fixation by perfusion, and processing for electron microscopy. From the earliest time examined, one and sometimes two rows of densely packed particles bound to some restricted plasma membrane microdomains that appeared as uncoated pits, and to plasmalemmal vesicles open on the luminal front. Morphometric analysis, using various albumin-gold concentrations, showed that the binding is saturable at a very low concentration of the ligand and short exposure. After 5 min, tracer-carrying vesicles appeared on the abluminal front, discharging their content into the subendothelial space. As a function of tracer concentration 1-10% of plasmalemmal vesicles contained Alb-Au particles in fluid phase; from 5 min on, multivesicular bodies were labeled by the tracer. Plasma membrane, coated pits, and coated vesicles were not significantly marked at any time interval. Heparin or high ionic strength did not displace the bound Alb-Au from vesicle membrane. No binding was obtained when Alb-Au was competed in situ with albumin or was injected in vivo. Gold complexes with fibrinogen, fibronectin, glucose oxidase, or polyethyleneglycol did not give a labeling comparable to that of albumin. These results suggest that on the capillary endothelia examined, the Alb-Au is adsorbed on specific binding sites restricted to uncoated pits and plasmalemmal vesicles. The tracer is transported in transcytotic vesicles across endothelium by receptor-mediated transcytosis, and to a lesser extent is taken up by pinocytotic vesicles. The existence of albumin receptors on these continuous capillary endothelia may provide a specific mechanism for the transport of albumin and other molecules carried by this protein.

The demonstration in vivo of specific binding sites for neuroleptic drugs in mouse brain

1977 ◽  
Vol 130 (1) ◽  
pp. 176-183 ◽  
Author(s):  
Volker Höllt ◽  
Andrzej Członkowski ◽  
Albert Herz
Keyword(s):  
Mouse Brain ◽  
Binding Sites ◽  
Specific Binding ◽  
Neuroleptic Drugs ◽  
Specific Binding Sites
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