scholarly journals The effect of salt concentration on the iron-binding properties of human transferrin

1982 ◽  
Vol 201 (3) ◽  
pp. 527-532 ◽  
Author(s):  
J Williams ◽  
N D Chasteen ◽  
K Moreton
Keyword(s):  
Salt Concentration ◽  
Binding Sites ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Iron Binding ◽  
Iron Release ◽  
Equilibrium Conditions ◽  
Binding Properties ◽  
Kinetics Of ◽  
Terminal Site

The salt dependence of the iron-binding properties of transferrin was studied by urea/polyacrylamide-gel electrophoresis. The distribution of iron between the N-terminal and C-terminal binding sites under equilibrium conditions and the rates of release of iron from the two sites were studied. It was found that salt increases the thermodynamic stability of iron binding in the N-terminal site relative to the C-terminal site. Similar behaviour is observed for the kinetics of iron release, where salt retards the rate of removal of iron from the N-terminal site but facilitates removal from the C-terminal site.

scholarly journals The distribution of iron between the metal-binding sites of transferrin human serum

1980 ◽  
Vol 185 (2) ◽  
pp. 483-488 ◽  
Author(s):  
J Williams ◽  
K Moreton
Keyword(s):  
Human Serum ◽  
Metal Binding ◽  
Binding Sites ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Iron Binding ◽  
Metal Binding Sites ◽  
Fresh Serum ◽  
Marked Preference ◽  
Terminal Site

The Makey & Seal [(1976) Biochim. Biophys. Acta 453, 250-256] method of polyacrylamide-gel electrophoresis in buffer containing 6 M-urea was used to determine the distribution of iron between the N-terminal and C-terminal iron-binding sites of transferrin in human serum. In fresh serum the two sites are unequally occupied; there is preferential occupation of the N-terminal site. On incubation of the serum at 37 degrees C the preference of iron for the N-terminal site becomes more marked. On storage of serum at −15 degrees C the iron distribution changes so that there is a marked preference for the C-terminal site. Dialysis of serum against buffer at pH 7.4 also causes iron to be bound much more strongly by the C-terminal than by the N-terminal site. The original preference for the N-terminal site can be resroted to the dialysed serum by addition of the diffusible fraction.

scholarly journals The iron-binding properties of hen ovotransferrin

1978 ◽  
Vol 173 (2) ◽  
pp. 533-539 ◽  
Author(s):  
J Williams ◽  
R W Evans ◽  
K Moreton
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Iron Binding ◽  
Alkaline Ph ◽  
Binding Properties ◽  
Partially Saturated ◽  
Isotope Method ◽  
Electrophoresis Method ◽  
Terminal Site ◽  
Double Isotope

1. The distribution of iron between the two iron-binding sites in partially saturated ovotransferrin was studied by labelling with 55Fe and 59Fe and by gel electrophoresis in a urea-containing buffer. 2. When iron is added in the form of chelate complexes at alkaline pH, binding occurs preferentially at the N-terminal binding site. In acid, binding occurs preferentially at the C-terminal site. 3. When simple iron donors (ferric and ferrous salts) are used the metal is distributed at random between the binding sites, as judged by the gel-electrophoresis method. The double-isotope method shows a preference of ferrous salts for the N-terminal site. 4. Quantitative treatment of the results of double-isotope labelling suggests that in the binding of iron to ovotransferrin at alkaline pH co-operative interactions between the sites occur. These interactions are apparently absent in the displacement of copper and in the binding of iron at acid pH.

scholarly journals Vertebrate lectins, Comparison of properties of beta-galactoside-binding lectins from tissues of calf and chicken.

1979 ◽  
Vol 81 (3) ◽  
pp. 528-537 ◽  
Author(s):  
E B Briles ◽  
W Gregory ◽  
P Fletcher ◽  
S Kornfeld
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Cellular Localization ◽  
Polyacrylamide Gel Electrophoresis ◽  
Thiol Group ◽  
Cross Reactivity ◽  
Cytoplasmic Localization ◽  
Binding Properties ◽  
Fluorescence Studies ◽  
Species Specific

Beta-galactoside-binding lectins were isolated from various calf tissues and from chicken hearts by affinity chromatography on asialofetuin-Sepharose, and were compared with respect to biochemical characteristics, binding properties, antigenic cross-reactivity, and cellular localization. The lectins are all thiol group-requiring, divalent cation-independent dimers, of apparent monomer mol wt 12,000 (calf lectins) or 13,000 (chicken lectin), and acidic pI. The calf lectins appear essentially identical by dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, amino acid composition, and radioimmunoassay, while the chicken lectin is distinctly different by these criteria. However, all of the lectins competed for the same binding sites on rabbit erythrocytes, and could be inhibited by the same saccharide haptens (notably lactose and thiodigalactoside). Immuno-fluorescence studies on several cultured cell lines revealed that the bovine and chicken lectins had primarily an intracellular cytoplasmic localization. The beta-galactoside-binding lectins of vertebrates appear to be species-specific rather than tissue-specific.

Platelet Microtubule Subunit Proteins

1979 ◽  
Vol 42 (05) ◽  
pp. 1630-1633 ◽  
Author(s):  
A G Castle ◽  
N Crawford
Keyword(s):  
Epithelial Cells ◽  
Gel Electrophoresis ◽  
Blood Platelets ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Lens Epithelial Cells ◽  
Molecular Weights ◽  
Kinetics Of ◽  
Microtubular Structures

SummaryBlood platelets contain microtubule proteins (tubulin and HMWs) which can be polymerised “in vitro” to form structures which resemble the microtubules seen in the intact platelet. Platelet tubulin is composed of two non-identical subunits a and p tubulin which have molecular weights around 55,000 but can be resolved in alkaline SDS-polyacrylamide gel electrophoresis. These subunits associate as dimers with sedimentation coefficients of about 5.7 S although it is not known whether the dimer protein is a homo- or hetero-dimer. The dimer tubulin binds the anti-mitotic drug colchicine and the kinetics of this binding are similar to those reported for neurotubulins. Platelet microtubules also contain two HMW proteins which appear to be essential and integral components of the fully assembled microtubule. These proteins have molecular weights greater than 200,000 daltons. Fluorescent labelled antibodies to platelet and brain tubulins stain long filamentous microtubular structures in bovine lens epithelial cells and this pattern of staining is prevented by exposing the cells to conditions known to cause depolymerisation of cell microtubules.

EXTRACELLULAR CALCIUM AND PLATELET GLYCOPROTEINS

1987 ◽  
Author(s):  
I Jabbal-Gill ◽  
G I Johnston ◽  
S Heptinstall
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Marked Decrease ◽  
Polyacrylamide Gel Electrophoresis ◽  
Specific Monoclonal Antibody ◽  
Alkaline Ph ◽  
Membrane Glycoproteins ◽  
Crossed Immunoelectrophoresis ◽  
The Stability ◽  
Ca Depletion

Platelet membrane glycoproteins lib and Ilia form Ca++-dependent heterodimer complexes that contain binding sites for fibrinogen and therefore are relevant to the ability of platelets to aggregate together. In this study we investigated the effects of extracellular Ca++ on the stability and expression of IIb-IIIa complexes using a IIb-IIIa complex-specific monoclonal antibody M148. Its specificity was examined using crossed immunoelectrophoresis: the antibody reacted only with intact IIb-IIIa complexes and not with either glycoprotein alone.SDS-polyacrylamide gel electrophoresis of immunoprecipitates of soluble glycoproteins that interacted with Ml48 showed that lib and Ilia were present as complexes in Ca++-depleted media at 25°C, pH7.4. However, Ca++-depletion at 37°C, pH7.4 or 37°C, pH8.7 or 25°C, pH8.7 caused dissociation of the complexThe effect of extracellular Ca++ on the expression of IIb-Illa complexes on the surface of intact platelets was studied by a technique which is based upon indirect binding of M148 using a fluorescent- labelled second antibody (FITC-RAM) and measuring the fluorescence per platelet using the FACS IV cytofluorometer. Intact platelets were incubated in Ca++-depleted media at 25°C, pH7.4 or 37°C, pH7.4 either (i) prior to or (ii) after adding M148. At 25°C increased M148-binding was observed, compared to the value prior to Ca++-depletion. This increased binding could be reversed by adding Ca++ back to the preparation. Under condition (i) at 37°C a marked decrease in M148 binding was observed, which could not be reversed by restoring Ca++, while under condition (ii) at 37°C the results were the same as at 25°C.Our studies demonstrate that (a) Ca++-depletion at 37°C and/or alkaline pH causes dissociation of the Ilb-IIIa complex (b) Ca++ depletion at 25°C possibly alters distribution of the complexes thereby increasing their availability to the antibody and (c) M148 prevents the dissociation of complexes in Ca++-depleted media at 37°C, possibly by holding lib and Ilia together

Binding Sites, Singly Bound States, and Conformation Coupling Shape GABA-Evoked Currents

2003 ◽  
Vol 89 (2) ◽  
pp. 871-883 ◽  
Author(s):  
Jerzy W. Mozrzymas ◽  
Andrea Barberis ◽  
Katarzyna Mercik ◽  
Ewa D. Z˙arnowska
Keyword(s):  
Binding Sites ◽  
Bound States ◽  
Time Course ◽  
Functional Coupling ◽  
Binding Properties ◽  
The Impact ◽  
Kinetics Of ◽  
Source Of Information ◽  
Respective Rate ◽  
Gating Scheme

The time course of GABA-evoked currents is the main source of information on the GABAAreceptor gating. Since the kinetics of these currents depends on the transitions between several receptor conformations, it is a major challenge to define the relations between current kinetics and the respective rate constants of the microscopic gating scheme. The aim of this study was to further explore the impact of different GABAA receptor conformations on the kinetics of currents elicited by ultra-fast GABA applications. We show that the rising phase and amplitude of GABA-evoked currents depend on desensitization and singly bound states. The occupancy of bound receptors depends not only on binding properties but also on opening/closing and desensitization. The impact of such functional coupling between channel states is critical in conditions of high non-equilibrium typical for synaptic transmission. The concentration dependence of the rising phase of the GABA-elicited current indicates positive cooperativity between agonist binding sites. We provide evidence that preequilibration at low GABA concentrations reduce GABA-evoked currents due to receptor trapping in a singly bound desensitized state.

scholarly journals Detection of disulphide bonds and localization of interchain linkages in the third (C3) and the fourth (C4) components of human complement

1986 ◽  
Vol 233 (3) ◽  
pp. 819-825 ◽  
Author(s):  
J Janatova
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Polyacrylamide Gel ◽  
Gamma Chain ◽  
Complement Components ◽  
The Third ◽  
Disulphide Bonds ◽  
Reduced State

Disulphide bonds contribute significantly to the maintenance of structural/functional integrity of many proteins. Therefore it was of interest to study the distribution and the effect of disulphides on conformation of complement components C3 and C4. These proteins are precursors of several fragments with various binding sites and distinct physiological functions. The constituents of C3c (beta, alpha 27, alpha 43) and those of C4c (beta, alpha 27, alpha 16, gamma) were investigated, since other fragments of C3 or C4 do not participate in interchain linkages. Inter-and intra-chain disulphide bonds in C3c and C4c were localized by using a modification of conventional SDS (sodium dodecyl sulphate)/polyacrylamide-gel electrophoresis such that the change in mobility of disulphide-bond-containing proteins can be detected throughout the transition from a non-reduced to a fully reduced state. Several forms of the alpha 43 fragment from C3, and of the gamma-chain of C4, with different mobilities can exist, depending on the number of intra-chain disulphide bonds reduced. The intermediates (heterodimers) generated by a partial reduction of C3c or C4c were characterized by two-dimensional SDS/polyacrylamide-gel electrophoresis performed in the absence, then in the presence, of beta-mercaptoethanol. The inter-chain linkages in C3c were determined to be beta-alpha 27 and alpha 27- alpha 43, thus indicating the presence of only one interchain bond in C3. The two interchain bonds in C4c are beta-alpha 27 and alpha 16-gamma. The third interchain bond in C4 (alpha 27-gamma, tentative) remains to be determined.

Acid and alkaline phosphatases of Capnocytophaga species. II. Isolation, purification, and characterization of the enzymes from Capnocytophaga ochracea

1983 ◽  
Vol 29 (10) ◽  
pp. 1361-1368 ◽  
Author(s):  
Thomas P. Poirier ◽  
Stanley C. Holt
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Alkaline Phosphatases ◽  
Purification And Characterization ◽  
Molecular Weights ◽  
Sds Page ◽  
Kinetics Of

Capnocytophaga ochracea acid (AcP; EC 3.1.3.2) and alkaline (AlP; EC 3.1.3.1) phosphatase was isolated by Ribi cell disruption and purified by sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS–PAGE.) Both phosphatases eluted from Sephadex G-150 consistent with molecular weights (migration) of 140 000 and 110 000. SDS–PAGE demonstrated a 72 000 and 55 000 subunit molecular migration for AcP and AlP, respectively. The kinetics of activity of purified AcP and AIP on p-nitrophenol phosphate and phosphoseryl residues of the phosphoproteins are presented.

Purification of α2-Antiplasmin by a Single-Step Affinity Chromatographic Procedure

1979 ◽  
Author(s):  
B Wiman
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Major Part ◽  
Polyacrylamide Gel Electrophoresis ◽  
Single Step ◽  
High Ionic Strength ◽  
Chromatographic Purification ◽  
Purification Method ◽  
Activity Measurements ◽  
Chromatographic Procedure

A new and efficient single-step purification method for human α2-antiplasmin has been elaborated. The method is based on the interaction between α2-antiplasmin and a fragment (LBSI) constituting the three NH2-terminal triple-loop structures in plasminogen produced by elastase digestion. This fragment has been purified and coupled to Sepharose and used for affinity chromatographic purification of α2-antiplasmin using plasminogen depleted plasma as starting material. After adsorption and washing at high ionic strength the α2-antiplasmin is specifically eluted with 6-aminohexanoic acid. The inhibitor preparation obtained in this way is over 90% pure as judged from SDS polyacrylamide gel electrophoresis and activity measurements. About 40-45 mg pure α2-antiplasmin per liter plasma is obtained representing a yield of about 60%. LBS-I Sepharose has much higher capacity for α2-antiplasmin and is also much more specific than plasminogen-Sepharose. Repetitive treatment of plasma with LBS I-Sepharose failed to adsorb the last 20% of α2-antiplasmin as judged by Laurell electrophoresis. This supports the recent finding ot Clemmensen (1979) on partially purified α2-antiplasmin that a form of the inhibitor with less affinity for the lysine-binding sites in plasminogen may exist, even in unfractionated plasma. The major part of this type of α2-antiplasmin is also a functional antiplasmin since it can form a complex with plasmin.

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