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.

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.

Kinetic analysis of rat parotid gland muscarinic receptors in vivo: comparison with brain and heart

1993 ◽  
Vol 264 (3) ◽  
pp. G541-G552
Author(s):  
Y. Hiramatsu ◽  
R. Kawai ◽  
R. C. Reba ◽  
T. R. Simon ◽  
B. J. Baum ◽  
...  
Keyword(s):  
Parotid Gland ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Muscarinic Acetylcholine Receptor ◽  
Binding Potential ◽  
Specific Binding Sites ◽  
Rat Parotid Gland ◽  
Rat Parotid

(RR)- and (SS)-quinuclidinyl iodobenzilate enantiomers [(RR)- and (SS)-IQNB, active and inert, respectively] have been synthesized for quantitative evaluation of muscarinic acetylcholine receptor (mAChR) binding. Pharmacokinetic approaches have not been used previously to assess in vivo IQNB binding in nonexcitable tissues. We have applied this method to examine mAChRs in rat parotid gland in comparison to those in brain and heart. Short-term infusion studies in vivo showed that the "instantaneous" reversible binding of (RR)- and (SS)-IQNB was high in the parotid (greater nonspecific binding potential), intermediate in the heart, and lowest in cortex and cerebellum. Long-term bolus injection experiments showed that the parotid gland mAChRs possessed a binding potential for receptor specific sites (380), which was intermediate between that of parietal cortex (930) and cerebellum (10) and greater than that of heart (165). In vitro binding to plasma membranes was generally consistent with the in vivo findings. In aggregate, these studies show that mAChRs can be evaluated in vivo in a nonexcitable tissue with the use of stereospecific ligands and a pharmacokinetic approach. The data suggest that IQNB, a mAChR antagonist, can identify characteristics of specific binding sites, which may reflect tissue differences.

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

2019 ◽  
Author(s):  
Erin Cutts ◽  
J. Barry Egan ◽  
Ian Dodd ◽  
Keith Shearwin
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Attachment Site ◽  
Binding Energies ◽  
Sequence Specificity ◽  
Binding Studies ◽  
Binding Model ◽  
Specific Binding Sites

AbstractThe 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.

Human chorionic gonadotropin binding sites in the human endometrium

1993 ◽  
Vol 129 (1) ◽  
pp. 15-19 ◽  
Author(s):  
S Bhattacharya ◽  
J Banerjee ◽  
S Sen ◽  
PR Manna
Keyword(s):  
Metal Ions ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Binding Sites ◽  
Binding Capacity ◽  
Specific Binding ◽  
Human Endometrium ◽  
Binding Characteristics ◽  
High Affinity ◽  
Specific Binding Sites

The existence of high-affinity and low-capacity specific binding sites for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) has been reported in porcine, rabbit and rat uteri. We have identified hCG binding sites in the human endometrium collected from 35–42-year-old ovulatory and anovulatory women. The binding characteristics of hCG to endometrial tissue preparations from ovulatory and anovulatory women showed saturability with high affinity and low capacity. Scatchard plot analysis showed the dissociation constant of specific binding sites in the ovulatory women to be 3.5 × 10−10 mol/l and in anovulatory women to be 3.1 × 10−10 mol/l. The maximum binding capacity varied considerably between ovulatory (3.85 nmol/kg protein) and anovulatory (6.12 nmol/kg protein) endometrium. Among the divalent metal ions tested (Zn2+, Mg2+, Mn2+, Ca2+—4 mol/l), Zn2+ effected a remarkable increase in [125I]hCG binding to the endometrium (p<0.005) whereas Mn2+ showed a marginal increase and other metal ions did not have any effect. Data obtained with human endometrium indicate an influence of the functional state of the ovary on [125I]hCG binding to endometrium.

Autoradiographic determination of dexamethasone binding sites along the rabbit nephron

1983 ◽  
Vol 244 (3) ◽  
pp. F325-F334 ◽  
Author(s):  
N. Farman ◽  
A. Vandewalle ◽  
J. P. Bonvalet
Keyword(s):  
Proximal Tubule ◽  
Binding Sites ◽  
Specific Binding ◽  
Rabbit Kidney ◽  
Nuclear Binding ◽  
Specific Binding Sites ◽  
In Vitro Incubation ◽  
Collecting Tubules

Specific binding sites of tritiated dexamethasone ([3H]dex) along the tubule of rabbit kidney were investigated using an autoradiographic method (dry film) on isolated tubular segments. After in vitro incubation of kidney pyramids with [3H]dex (0.15-53 nM) in the presence or absence of an excess (X200) of unlabeled dexamethasone, tubular segments were microdissected and processed for autoradiography. A quantitative analysis of specific labeling over cytoplasm and nuclei was performed. Specific nuclear binding was observed in all tubular segments beyond the pars recta. This binding was dose dependent and reached much higher values than those reported for aldosterone. In the proximal tubule, the specific labeling was also high but remained mostly cytoplasmic. The meaning of these drastically different intracellular localizations is still open to interpretation. Autoradiography was performed after in vivo injection of [3H]dex and [3H]aldosterone. The results were not different from those described here for dexamethasone and from those previously reported for aldosterone after in vitro incubation. We conclude that specific nuclear binding sites for dexamethasone range over the nephron except for proximal tubule, with no great difference among segments, in contrast to specific sites for aldosterone, which are restricted to distal and cortical collecting tubules. The exact significance of the proximal cytoplasmic specific binding of [3H]dex remains to be determined.

Brain Specific Benzodiazepine Receptors

1978 ◽  
Vol 133 (3) ◽  
pp. 249-260 ◽  
Author(s):  
Claus Bræstrup ◽  
Richard F. Squires
Keyword(s):  
Binding Sites ◽  
Neuronal Degeneration ◽  
Specific Binding ◽  
Benzodiazepine Receptors ◽  
Clinical Effects ◽  
Single Class ◽  
Specific Binding Sites ◽  
Benzodiazepine Binding Sites

SummaryBrain membranes from rat and human contain a single class of brain specific binding sites for pharmacologically and clinically active benzodiazepines. There is good correlation between the pharmacological effects of benzodiazepines and the affinity for the 3H-diazepam binding site.Benzodiazepine binding sites are not present on glial cells. Selective neuronal degeneration experiments in rats indicate a neuronal localization. 3H-Flunitrazepam is a very suitable ligand for affinity binding and it binds to the same class of binding sites as 3H-diazepam.Our results indicate that the in vitro3H-diazepam and 3H-flunitrazepam binding sites are the receptors which in vivo mediate various pharmacological and clinical effects of benzodiazepines.

Progastrin1–80stimulates growth of intestinal epithelial cells in vitro via high-affinity binding sites

2003 ◽  
Vol 284 (2) ◽  
pp. G328-G339 ◽  
Author(s):  
P. Singh ◽  
X. Lu ◽  
S. Cobb ◽  
B. T. Miller ◽  
N. Tarasova ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Binding Sites ◽  
Intestinal Epithelial Cells ◽  
Full Length ◽  
Intestinal Epithelial ◽  
Growth Effects ◽  
High Affinity ◽  
Significant Difference

Proliferation and carcinogenesis of the large intestinal epithelial cells (IEC) cells is significantly increased in transgenic mice that overexpress the precursor progastrin (PG) peptide. It is not known if the in vivo growth effects of PG on IEC cells are mediated directly or indirectly. Full-length recombinant human PG (rhPG1–80) was generated to examine possible direct effects of PG on IEC cells. Surprisingly, rhPG (0.1–1.0 nM) was more effective than the completely processed gastrin 17 (G17) peptide as a growth factor. Even though IEC cells did not express CCK1and CCK2receptors (-R), fluorescently labeled G17 and Gly-extended G17 (G-Gly) were specifically bound to the cells, suggesting the presence of binding proteins other than CCK1-R and CCK2-R on IEC cells. High-affinity ( Kd= 0.5–1.0 nM) binding sites for125I-rhPG were discovered on IEC cells that demonstrated relative binding affinity for gastrin-like peptides in the order PG ≥ COOH-terminally extended G17 ≥ G-Gly > G17 > *CCK-8 (* significant difference; P< 0.05). In conclusion, our studies demonstrate for the first time direct growth effects of the full-length precursor peptide on IEC cells in vitro that are apparently mediated by the high-affinity PG binding sites that were discovered on these cells.

Sign in / Sign up

Export Citation Format

Share Document