Search results for "binding"
showing 10 items of 3896 documents
Distribution of chlorpromazine in a simplified blood influenced by various drugs
1973
The binding of chlorpromazine to erythrocytes and to albumin as influenced by other drugs was studied in a simplified blood (31.5±0.3% bovine erythrocytes, 4 g-% bovine serum albumin in 0.02 M phosphate buffer solution containing 0.15 M NaCl). the total concentration of chlorpromazine in the simplified blood was 10−4 M, the concentration of the displacing drugs was 10−3 M. After an incubation period of 3 h at 22° C the chlorpromazine concentration was determined in the albumin solution after centrifugation of the blood at 3000×g and in the aqueous phase after ultracentrifugation at 150000×g. Under control conditions 68.1±0.9% of chlorpromazine was bound to the erythrocytes, 28.5±0.9% was bo…
The molecular basis of the low hemolytic activity of C4 molecules from low-C4 mice with IgM-coated erythrocytes.
1989
This study investigated the origin of the different hemolytic activity of two allotypes of murine C4, C4H (C4-high) and C4L (C4-low) in the presence of IgM-coated erythrocytes. C4H displayed a threefold higher hemolytic titer (expressed in hemolytic units/microgram protein) than C4L. No difference was found between c4H and C4L either in stability at 37 degrees C at different pH values and in the rate of C4H and C4L hydrolysis by activated Cl. The major functional difference was found in the covalent binding capacity to IgM-coated erythrocytes, with the amount of C4H bound being about threefold higher than that of C4L. A marked difference in the reactivity of the C4b fragment of C4H and C4L …
Involvement of carboxyl groups in chloride transport and reversible DIDS binding to band 3 protein in human erythrocytes
2011
AbstractNoncovalent DIDS binding to Band 3 (AE1) protein in human erythrocyte membranes, modified by non-penetrating, water soluble 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)-carbodiimide iodide (EAC), was studied at 0°C in the presence of 165 mM KCl. Under experimental conditions applied up to (48 ± 5) % of irreversible chloride self-exchange inhibition was observed. The apparent dissociation constant, KD, for “DIDS-Band 3” complex, determined from the chloride transport experiments, was (34 ± 3) nM and (80 ± 12) nM for control and EAC-treated resealed ghosts, respectively. The inhibition constant, Ki, for DIDS was (35 ± 6) nM and (60 ± 8) nM in control and EAC-treated ghosts, respectively. T…
Oligomerization and hemolytic properties of the C-terminal domain of pyolysin, a cholesterol-dependent cytolysin
2013
Pyolysin (PLO) belongs to the homologous family of the cholesterol- dependent cytolysins (CDCs), which bind to cell membranes containing cholesterol to form oligomeric pores of large size. The CDC monomer structure consists of 4 domains. Among these, the C-terminal domain 4 has been implicated in membrane binding of the monomer, while the subsequent processes of oligomerization and membrane insertion have primarily been assigned to other domains of the molecule. Recombinantly expressed or proteolytic fragments that span domain 4 of the CDCs streptolysin O and perfringolysin O bind to membranes but fail to oligomerize, and they inhibit the activity of the respective wild-type toxins. We repo…
Expression of Active Streptolysin O in Escherichia coli as a Maltose-Binding-Protein-Streptolysin-O Fusion Protein. The N-Terminal 70 Amino Acids are…
1996
Streptolysin 0 (SLO) is the prototype of a family of cytolysins that consists of proteins which bind to cholesterol and form very large transmembrane pores. Structure/function studies on the pore-forming cytolysin SLO have been complicated by the proteolytic inactivation of a substantial portion of recombinant SLO (rSLO) expressed in Escherichia coli. To overcome this problem, translational fusions between the E. coli maltose-binding protein (MBP) gene and SLO were constructed, using the vectors pMAL-p2 and pMAL-c2. MBP-SLO fusion proteins were degraded if secreted into the E. coli periplasm, but intact, soluble MBP-SLO fusion proteins were produced at high levels in the cytoplasm. Active S…
Evidence that clustered phosphocholine head groups serve as sites for binding and assembly of an oligomeric protein pore.
2006
High susceptibility of rabbit erythrocytes toward the pore-forming action of staphylococcal alpha-toxin correlates with the presence of saturable, high affinity binding sites. All efforts to identify a protein or glycolipid receptor have failed, and the fact that liposomes composed solely of phosphatidylcholine are efficiently permeabilized adds to the enigma. A novel concept is advanced here to explain the puzzle. We propose that low affinity binding moieties can assume the role of high affinity binding sites due to their spatial arrangement in the membrane. Evidence is presented that phosphocholine head groups of sphingomyelin, clustered in sphingomyelin-cholesterol microdomains, serve th…
Cysteine-Specific Radioiodination of Proteins with Fluorescein Maleimide
1997
A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing condit…
Role of β1H for the binding of C3b-coated particles to human lymphoid and phagocytic cells
1981
Coating of EAC14oxy23b with highly purified human serum beta 1H globulin (beta 1H) led to acceleration of rosette formation with human peripheral blood lymphocytes (PBL), tonsil lymphocytes, B lymphoblastoid (Raji) cells, granulocytes and monocytes. This reaction was discernible from C3bi-dependent rosette formation. Enhancement of rosette formation of C3b cells by beta 1H was most effective at limiting amounts of C3 per EAC14oxy23b. The beta 1H effect was not due to trace contamination with C3b inactivator. beta 1H-dependent rosette formation with the various lymphoid and phagocytic cells could be suppressed by the F(ab')2 fragment of anti-beta 1H suggesting beta 1H-mediated binding of bet…
Gcn5p is involved in the acetylation of histone H3 in nucleosomes.
1997
Abstract Enzymatic extracts from a gcn5 mutant and wild-type strains of Saccharomyces cerevisiae were chromatographically fractionated and the histone acetyltransferase activities compared. When free histones were used as substrate, extracts from wild-type cells showed two peaks of activity on histone H3 but extracts from gcn5 mutant cells showed only one. With nucleosomes as substrate, the histone acetyltransferase activities present in extracts from the gcn5 mutant strain were not able to modify H3 whereas wild-type cell extracts acetylated intensely this histone. The activity that acetylated nucleosome-bound H3 behaved as a 170-kDa complex. We suggest that Gcn5p represents a catalytic su…
Ligand-Binding Cooperativity Effects in Polymer-Protein Conjugation.
2019
We present an electron paramagnetic resonance (EPR) spectroscopic characterization of structural and dynamic effects that stem from post-translational modifications of bovine serum albumin (BSA), an established model system for polymer-protein conjugation. Beyond the typical drug delivery and biocompatibility aspect of such systems, we illustrate the causes that alter internal dynamics and therefore functionality in terms of ligand-binding to the BSA protein core. Uptake of the paramagnetic fatty acid derivative 16-doxyl stearic acid by several BSA-based squaric acid macroinitiators and polymer-protein conjugates was studied by EPR spectroscopy, aided by dynamic light scattering (DLS) and z…