scholarly journals Ligand size is a major determinant of high-affinity binding of fucose- and galactose-exposing (lipo)proteins by the hepatic fucose receptor

1994 ◽  
Vol 299 (1) ◽  
pp. 291-296 ◽  
Author(s):  
E A Biessen ◽  
H F Bakkeren ◽  
D M Beuting ◽  
J Kuiper ◽  
T J Van Berkel
Keyword(s):  
Kupffer Cell ◽  
Kupffer Cells ◽  
Asialoglycoprotein Receptor ◽  
Major Determinant ◽  
Affinity Binding ◽  
Binding Studies ◽  
High Affinity Binding ◽  
High Affinity ◽  
Parenchymal Liver

Previous in vivo studies have demonstrated that small galactose-exposing particles are preferentially internalized by the asialoglycoprotein receptor on the parenchymal liver cell and large particles by the galactose-particle receptor on the Kupffer cell. In this study, we have investigated using in vitro binding studies whether the affinity for either receptor is affected by the ligand size. The asialoglycoprotein receptor appeared to bind and process lactosylated proteins irrespective of their size. In contrast, recognition of galactose-exposing proteins by the galactose-particle receptor on the Kupffer cell was strongly dependent on size. The affinity increased 3000-fold with protein sizes increasing from 5 to 15 nm, reaching its maximum at approx. 1 nM for ligands larger than 15 nm. Apparently, the preferential in vivo uptake of large galactose-exposing ligands by Kupffer cells does not result from an inability of the parenchymal liver cells to internalize these ligands, but from the high affinity of large ligands for the galactose-particle receptor and the strategic anatomical localization of the Kupffer cells in the liver. In the preceding paper [Kuiper, Bakkeren, Biessen and Van Berkel (1994) Biochem. J. 299, 285-290] the galactose-particle receptor on the Kupffer cell was suggested to be identical with the fucose receptor. 125I-Lac-LDL-binding studies clearly showed that the galactose-particle receptor exhibited high-affinity binding of fucose-exposing proteins also. The affinity of fucosylated proteins for the galactose-particle receptor was greatly affected by ligand size. The above data strongly support the hypothesis that the galactose-particle receptor is identical with the fucose receptor. The size of neoglycoproteins can be appreciated as a new major determinant of affinity for the fucose receptor.

Ca2+ channel antagonist actions in bladder smooth muscle: comparative pharmacologic and [3H]nitrendipine binding studies

1985 ◽  
Vol 63 (5) ◽  
pp. 453-462 ◽  
Author(s):  
F. B. Yousif ◽  
G. T. Bolger ◽  
A. Ruzycky ◽  
D. J. Triggle
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Smooth Muscles ◽  
Affinity Binding ◽  
Induced Responses ◽  
Bladder Smooth Muscle ◽  
Binding Studies ◽  
Tonic Component ◽  
High Affinity Binding ◽  
High Affinity

The actions of a series of 15 Ca2+ channel antagonists including D-6(X), nifedipine, and diltiazem were examined against K+ depolarization and muscarinic receptor induced responses in guinea pig bladder smooth muscle. Responses of bladder are very dependent upon extracellular Ca2+ and sensitive to the Ca2+ channel antagonists, the tonic component more than the phasic component of response. Regardless of stimulant, K+ or methylfurmethide (MF), or component of response, the same rank order of antagonist activities is expressed, suggestive of a single structure–activity relationship and the existence of a single category of binding site which may, however, exist in several affinity states. High affinity binding of [3H]nitrendipine (KD = 1.1 × 10−10 M) occurs in bladder membranes, and similar high affinity binding was found in microsomal preparations from other smooth muscles including guinea pig and rat lung, rat vas deferens, uterus, and stomach. [3H]nitrendipine binding in the bladder was sensitive to displacement by other 1,4-dihydropyridines, paralleling their pharmacologic activities and showing excellent agreement with binding data previously obtained for guinea pig ileal smooth muscle. Comparison of pharmacologic data for inhibition of K+- and MF-induced responses by a common series of Ca2+ channel antagonists in bladder and ileum revealed excellent correlations. Neither pharmacologic nor binding studies suggest significant differences in Ca2+ channel antagonist properties in smooth muscle from bladder and intestine.

scholarly journals The interaction between human blood-coagulation factor VIII and von Willebrand factor. Characterization of a high-affinity binding site on factor VIII

1989 ◽  
Vol 257 (3) ◽  
pp. 679-683 ◽  
Author(s):  
A Leyte ◽  
M P Verbeet ◽  
T Brodniewicz-Proba ◽  
J A Van Mourik ◽  
K Mertens
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Coagulation Factor ◽  
Affinity Binding ◽  
Binding Studies ◽  
High Affinity Binding ◽  
High Affinity ◽  
Human Factor Viii ◽  
Von Willebrand ◽  
Willebrand Factor

The interaction between human Factor VIII and immobilized multimeric von Willebrand Factor (vWF) was characterized. Equilibrium binding studies indicated the presence of multiple classes of Factor VIII-binding sites on vWF. The high-affinity binding (Kd = 2.1 x 10(-10) M) was restricted to only 1-2% of the vWF subunits. Competition studies with monoclonal antibodies with known epitopes demonstrated that the Factor VIII sequence Lys1673-Arg1689 is involved in the high-affinity interaction with vWF.

High-Affinity Binding of Fibronectin to Cultured Kupffer Cells

1990 ◽  
Vol 48 (5) ◽  
pp. 426-437 ◽  
Author(s):  
Pina M. Cardarelli ◽  
Frank A. Blumenstock ◽  
Paula J. McKeown-Longo ◽  
Thomas M. Saba ◽  
Joseph E. Mazurkiewicz ◽  
...  
Keyword(s):  
Kupffer Cells ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity

scholarly journals Mutations in the DG Loop of Adenovirus Type 5 Fiber Knob Protein Abolish High-Affinity Binding to Its Cellular Receptor CAR

1999 ◽  
Vol 73 (11) ◽  
pp. 9508-9514 ◽  
Author(s):  
Ian Kirby ◽  
Elizabeth Davison ◽  
Andrew J. Beavil ◽  
Cecilia P. C. Soh ◽  
Thomas J. Wickham ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Receptor Binding ◽  
Adenovirus Type ◽  
Cellular Receptor ◽  
Affinity Binding ◽  
Cd Spectra ◽  
Binding Studies ◽  
High Affinity Binding ◽  
High Affinity ◽  
Adenovirus Type 5

ABSTRACT The amino acid residues in adenovirus type 5 (Ad5) fiber that interact with its cellular receptor, the coxsackie B virus and Ad receptor (CAR), have not been defined. To investigate this, multiple mutations were constructed in the region between residues 479 and 497 in Ad5 fiber (β-strands E and F and the adjacent region of the DG loop). The effects of these mutations on binding to CAR were determined by use of cell-binding competition experiments, surface plasmon resonance, and direct binding studies. The mutation effects on the overall folding and secondary structure of the protein were assessed by circular dichroism (CD) spectroscopy. Deletions of two consecutive amino acids between residues 485 and 493 abolished high-affinity binding to CAR; the CD spectra indicated that although there was no disruption of the overall folding and secondary structure of the protein, local conformational changes did occur. Moreover, single site mutations in this region of residues with exposed, surface-accessible side chains, such as Thr492, Asn493, and Val495, had no effect on receptor binding, which demonstrates that these residues are not in contact with CAR themselves. This implies the involvement of residues in neighboring loop regions. Replacement of the segment containing the two very short β-strands E and F and the turn between them (residues 479 to 486) with the corresponding sequence from Ad3 (βEFAd3→5 mutation) resulted in the loss of receptor binding. The identical CD spectra for βEFAd3→5 and wild-type proteins suggest that these substitutions caused no conformational rearrangement and that the loss of binding may thus be due to the substitution of one or more critical contact residues. These findings have implications for our understanding of the interaction of Ad5 fiber with CAR and for the construction of targeted recombinant Ad5 vectors for gene therapy purposes.

RAT MYOMETRIAL ACTIVITY IN VIVO: EFFECTS OF OESTRADIOL-17β AND PROGESTERONE IN RELATION TO THE CONCENTRATIONS OF CYTOPLASMIC PROGESTERONE RECEPTORS

1978 ◽  
Vol 78 (1) ◽  
pp. 103-117 ◽  
Author(s):  
SANDRA J. DOWNING ◽  
S. J. LYE ◽  
JANE M. C. BRADSHAW ◽  
D. G. PORTER
Keyword(s):  
Binding Protein ◽  
Progesterone Receptors ◽  
Affinity Binding ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
High Affinity Binding ◽  
High Affinity ◽  
Repeated Doses ◽  
In Vivo Effects

The amplitude, frequency and rate of rise of intra-uterine pressure cycles in rats (postpartum, ovariectomized) were unaffected by treatment with progesterone. Amplitude was also unaffected by a combination of treatments with progesterone and oestradiol-17β, which was adequate to ensure the survival of 84% of foetuses in ovariectomized pregnant rats. The failure of progesterone to influence myometrial activity could not be attributed to a lack of 'true' progesterone receptors since these were present in the myometria of the test animals in concentrations exceeding those of oestrous animals. Evidence was obtained which suggested that a high-affinity binding protein, different from the 'true' receptor may predominate in the myometrium of the pregnant rat. Oestradiol-17β in single or repeated doses of from 0·25 to 5 μg, however, was found to reduce the frequency of pressure cycles but to increase significantly their rate of rise of pressure. There was a latency of 6–8 h in these effects of oestradiol. The possibility that inhibition of the myometrium by oestrogen may play a part in the preparation for parturition is discussed.

scholarly journals The TorR High-Affinity Binding Site Plays a Key Role in Both torR Autoregulation and torCADOperon Expression in Escherichia coli

2000 ◽  
Vol 182 (4) ◽  
pp. 961-966 ◽  
Author(s):  
Mireille Ansaldi ◽  
Gwénola Simon ◽  
Michèle Lepelletier ◽  
Vincent Méjean
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Binding Sites ◽  
Response Regulator ◽  
Regulatory System ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity ◽  
High Affinity Binding Site

ABSTRACT In the presence of trimethylamine N-oxide (TMAO), the TorS-TorR two-component regulatory system induces thetorCAD operon, which encodes the TMAO respiratory system ofEscherichia coli. The sensor protein TorS detects TMAO and transphosphorylates the response regulator TorR which, in turn, activates transcription of torCAD. The torRgene and the torCAD operon are divergently transcribed, and the short torR-torC intergenic region contains four direct repeats (the tor boxes) which proved to be TorR binding sites. The tor box 1-box 2 region covers thetorR transcription start site and constitutes a TorR high-affinity binding site, whereas box 3 and box 4 correspond to low-affinity binding sites. By using torR-lacZ operon fusions in different genetic backgrounds, we showed that thetorR gene is negatively autoregulated. Surprisingly, TorR autoregulation is TMAO independent and still occurs in atorS mutant. In addition, this negative regulation involves only the TorR high-affinity binding site. Together, these data suggest that phosphorylated as well as unphosphorylated TorR binds the box 1-box 2 region in vivo, thus preventing RNA polymerase from binding to the torR promoter whatever the growth conditions. By changing the spacing between box 2 and box 3, we demonstrated that the DNA motifs of the high- and low-affinity binding sites must be close to each other and located on the same side of the DNA helix to allow induction of the torCAD operon. Thus, prior TorR binding to the box 1-box 2 region seems to allow cooperative binding of phosphorylated TorR to box 3 and box 4.

scholarly journals Platelet-activating factor (PAF-acether) induces high- and low-affinity binding of fibrinogen to human platelets via independent mechanisms

1986 ◽  
Vol 240 (2) ◽  
pp. 403-412 ◽  
Author(s):  
E Kloprogge ◽  
J W Akkerman
Keyword(s):  
Platelet Activation ◽  
Binding Sites ◽  
Platelet Activating Factor ◽  
Human Platelets ◽  
Affinity Binding ◽  
Binding Studies ◽  
High Affinity Binding ◽  
High Affinity ◽  
Fibrinogen Binding ◽  
A Minor

When human platelets are incubated with 500 nM-PAF-acether (platelet-activating factor. 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) under equilibrium conditions (60 min, 22 degrees C, non-stirred suspensions), two classes of fibrinogen binding sites are exposed: one class with a high affinity [Kd (7.2 +/- 2.1) X 10(-8) M, 2367 +/- 485 sites/platelet, n = 9] and one class with a low affinity [Kd (5.9 +/- 2.4) X 10(-7) M, 26972 +/- 8267 sites/platelet]. Preincubation with inhibitors of cyclo-oxygenase (acetylsalicylic acid, indomethacin) or thromboxane synthetase (UK 38.485) completely abolishes high-affinity binding, leaving low-affinity binding unchanged. In contrast, ADP scavengers (phosphocreatine/creatine kinase or phosphoenol pyruvate/pyruvate kinase) completely prevent low-affinity binding, leaving high-affinity binding unaltered. Initial binding studies (2-10 min incubation) confirm these findings with a major part of the binding being sensitive to ADP scavengers, a minor part sensitive to indomethacin and complete blockade with both inhibitors. Increasing the temperature to 37 degrees C decreases the number of low affinity-binding sites 6-fold without changing high-affinity binding. Aggregation, measured as the rate of single platelet disappearance, then depends on high-affinity binding at 10 nM-fibrinogen or less, whereas at 100 nM-fibrinogen or more low-affinity binding becomes predominant. These findings point at considerable platelet activation during binding experiments. However, arachidonate metabolism [(3H]arachidonate mobilization and thromboxane synthesis) and secretion [(14C]serotonin and beta-thromboglobulin) are about 10% or less of the amounts found under optimal conditions (5 units of thrombin/ml 37 degrees C, stirring). We conclude that PAF-acether induces little platelet activation under binding conditions. The amounts of thromboxane A2 and secreted ADP, however, are sufficient for initiating high- and low-affinity fibrinogen binding via mutually independent mechanisms.

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