scholarly journals beta1 Integrin and alpha-dystroglycan binding sites are localized to different laminin-G-domain-like (LG) modules within the laminin alpha5 chain G domain

2003 ◽  
Vol 371 (2) ◽  
pp. 289-299 ◽  
Author(s):  
Hao YU ◽  
Jan F. TALTS
Keyword(s):  
Binding Sites ◽  
Mammalian Cells ◽  
Solid Phase ◽  
Polyclonal Antibodies ◽  
Matrix Proteins ◽  
High Affinity ◽  
Immunofluorescence Studies ◽  
Beta1 Integrin ◽  
Alpha Dystroglycan ◽  
Tandem Arrays

Laminins are a group of extracellular-matrix proteins important in development and disease. They are heterotrimers, and specific domains in the different chains have specialized functions. The G domain of the α5 chain has now been produced in transfected mammalian cells as single modules and two tandem arrays, α5LG1–3 and α5LG4–5 (LG is laminin G domain-like). Using these fragments we produced specific polyclonal antibodies functional in immunoblotting and immunofluorescence studies and in solid-phase assays. Both α5LG tandem arrays had physiologically relevant affinities for sulphated ligands such as heparin and sulphatides. Cells adhered to these fragments and acquired a spread morphology when plated on α5LG1–3. Binding of integrins α3β1 and α6β1 was localized to the α5LG1–3 modules, and α-dystroglycan binding was localized to the α5LG4–5 modules, thus locating these activities to different LG modules within the laminin α5 G domain. However, both these activities were of relatively low affinity, indicating that integrin-mediated cell adhesion to the laminin 10/11 α5G domain depends on contributions from the other chains of the heterotrimer and that high-affinity α-dystroglycan binding could be dependent on specific Ca2+-ion-co-ordinating amino acids absent from α5LG4–5.

Hormonal dependency of cerebral meningiomas

1990 ◽  
Vol 73 (5) ◽  
pp. 743-749 ◽  
Author(s):  
Uwe M. H. Schrell ◽  
Eric F. Adams ◽  
Rudolf Fahlbusch ◽  
Robert Greb ◽  
Gustav Jirikowski ◽  
...  
Keyword(s):  
Estrogen Receptors ◽  
Binding Sites ◽  
Solid Phase ◽  
Steroid Receptors ◽  
Progesterone Receptors ◽  
Nuclear Compartment ◽  
Content Type ◽  
High Affinity ◽  
Immunohistochemical Techniques ◽  
Fine Print

✓ Female sex steroid receptors were examined in 50 human cerebral meningiomas. For estrogen receptors, high-affinity binding sites (dissociation constant (Kd): 0.05 to 0.2 nM) were found in the cytosolic fraction with a capacity of less than 4 fmol/mg protein in 10 meningiomas using a dextran-coated charcoal (DCC) assay. In the same cytosolic fraction, the solid-phase enzyme immunoassay revealed only one cytosol with a positive colorimetric reaction equal to 5 fmol/mg protein. However, in the nuclear compartment, none of the tumors stained positively for estrogen receptors with immunohistochemical techniques. In addition, the most convincing evidence for the absence of estrogen receptors was obtained by in situ hybridization using an oligonucleotide probe complementary to a fraction of the human receptor messenger ribonucleic acid (mRNA). In none of the 50 meningiomas was the expression of estrogen mRNA coding for the estrogen receptor detected. For progesterone receptors, high-affinity binding sites (Kd: 0.3 to 2.6 nM) were found in 49 of the 50 tumors using a DCC assay. In the same cytosols, solid-phase enzyme immunoassay revealed that each tumor was positive for progesterone receptors. However, in the nuclear compartment, only five tumors had partially positive staining for progesterone receptors with immunohistochemical techniques. Within the confines of this study, it is concluded that: 1) the estrogen receptor is generally absent in meningioma tissue, and 2) the progesterone receptor is mainly absent in the nuclear compartment, leading to the conclusion that the cytosolic progesterone receptor may be an inactive form. This study suggests that female sex steroid receptors are not primarily involved in the proliferative rate of cerebral meningiomas and that they are of no current significance as markers for adjuvant medical therapy of most meningiomas.

scholarly journals Peptide Scanning of SARS-CoV and SARS-CoV-2 Spike Protein Subunit 1 Reveals Potential Additional Receptor Binding Sites

2021 ◽  
Author(s):  
Weilin Lin ◽  
Jannatul Rafeya ◽  
Vanessa Roschewitz ◽  
David Smith ◽  
Adrian Keller ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Binding Sites ◽  
Neutralizing Antibodies ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Spike Protein ◽  
Loss Of Function ◽  
Protein Subunit ◽  
Viral Attachment ◽  
High Affinity

The binding of SARS-CoV and SARS-CoV-2 to the ACE2 receptor on human cells is mediated by the spike protein subunit 1 (S1) on the virus surfaces, while the receptor binding domains (RBDs) of S1 are the major determinants for the interaction with ACE2 and dominant targets of neutralizing antibodies. However, at the virus-host interface, additional biomolecular interactions, although being relatively weak in affinity and low in specificity, could also contribute to viral attachment and play important roles in gain- or loss-of-function mutations. In this work, we performed a peptide scanning of the S1 domains of SARS-CoV and SARS-CoV-2 by synthesizing 972 16-mer native and mutated peptide fragments using a high throughput in situ array synthesis technology. By probing the array using fluorescently labelled ACE2, a number of previously unknown potential receptor binding sites of S1 have been revealed. 20 peptides were synthesized using solid phase peptide synthesis, in order to validate and quantify their binding to ACE2. Four ACE2-binding peptides were selected, to investigate whether they can be assembled through a biotinylated peptide/neutravidin system to achieve high affinity to ACE2. A number of constructs exhibited high affinity to ACE2 with Kd values of pM to low nM.

High Affinity Binding Sites for Activated Protein C and Protein C on Cultured Human Umbilical Vein Endothelial Cells

1994 ◽  
Vol 72 (03) ◽  
pp. 465-474 ◽  
Author(s):  
Neelesh Bangalore ◽  
William N Drohan ◽  
Carolyn L Orthner
Keyword(s):  
Binding Sites ◽  
Protein C ◽  
Umbilical Vein ◽  
Activated Protein C ◽  
Affinity Binding ◽  
Cell Binding ◽  
High Affinity Binding ◽  
High Affinity ◽  
Gla Domain ◽  
Umbilical Vein Endothelial Cells

SummaryActivated protein C (APC) is an antithrombotic serine proteinase having anticoagulant, profibrinolytic and anti-inflammatory activities. Despite its potential clinical utility, relatively little is known about its clearance mechanisms. In the present study we have characterized the interaction of APC and its active site blocked forms with human umbilical vein endothelial cells (HUVEC). At 4° C 125I-APC bound to HUVEC in a specific, time dependent, saturable and reversible manner. Scatchard analysis of the binding isotherm demonstrated a Kd value of 6.8 nM and total number of binding sites per cell of 359,000. Similar binding isotherms were obtained using radiolabeled protein C (PC) zymogen as well as D-phe-pro-arg-chloromethylketone (PPACK) inhibited APC indicating that a functional active site was not required. Competition studies showed that the binding of APC, PPACK-APC and PC were mutually exclusive suggesting that they bound to the same site(s). Proteolytic removal of the N-terminal γ-carboxyglutamic acid (gla) domain of PC abolished its ability to compete indicating that the gla-domain was essential for cell binding. Surprisingly, APC binding to these cells appeared to be independent of protein S, a cofactor of APC generally thought to be required for its high affinity binding to cell surfaces. The identity of the cell binding site(s), for the most part, appeared to be distinct from other known APC ligands which are associated with cell membranes or extracellular matrix including phospholipid, thrombomodulin, factor V, plasminogen activator inhibitor type 1 (PAI-1) and heparin. Pretreatment of HUVEC with antifactor VIII antibody caused partial inhibition of 125I-APC binding indicating that factor VIII or a homolog accounted for ∼30% of APC binding. Studies of the properties of surface bound 125I-APC or 125I-PC and their fate at 4°C compared to 37 °C were consistent with association of ∼25% of the initially bound radioligand with an endocytic receptor. However, most of the radioligand appeared not to be bound to an endocytic receptor and dissociated rapidly at 37° C in an intact and functional state. These data indicate the presence of specific, high affinity binding sites for APC and PC on the surface of HUVEC. While a minor proportion of binding sites may be involved in endocytosis, the identity and function of the major proportion is presently unknown. It is speculated that this putative receptor may be a further mechanisms of localizing the PC antithrombotic system to the vascular endothelium.

Synthesis and Screening of A DNA-Encoded Library of Non-Peptidic Macrocycles

2020 ◽  
Author(s):  
Eric Koesema ◽  
Animesh Roy ◽  
Nicholas G. Paciaroni ◽  
Thomas Kodadek
Keyword(s):  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Cell Permeability ◽  
Phase Synthesis ◽  
Protein Ligands ◽  
High Affinity ◽  
Scaffold Diversity

There is considerable interest in the development of libraries of non-peptidic macrocycles as a source of ligands for difficult targets. We report here the solid-phase synthesis of a DNA-encoded library of several hundred thousand thioether-linked macrocycles. The library was designed to be highly diverse with respect to backbone scaffold diversity and to minimize the number of amide N-H bonds, which compromise cell permeability. The utility of the library as a source of protein ligands is demonstrated through the isolation of compounds that bind streptavidin, a model target, with high affinity.

scholarly journals Novel Three-Finger Neurotoxins from Naja melanoleuca Cobra Venom Interact with GABAA and Nicotinic Acetylcholine Receptors

Toxins ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 164
Author(s):  
Lina Son ◽  
Elena Kryukova ◽  
Rustam Ziganshin ◽  
Tatyana Andreeva ◽  
Denis Kudryavtsev ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Gabaa Receptors ◽  
Binding Sites ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine ◽  
High Affinity ◽  
Central Loop ◽  
Acetylcholine Binding Proteins ◽  
Α7 Nachrs

Cobra venoms contain three-finger toxins (TFT) including α-neurotoxins efficiently binding nicotinic acetylcholine receptors (nAChRs). As shown recently, several TFTs block GABAA receptors (GABAARs) with different efficacy, an important role of the TFTs central loop in binding to these receptors being demonstrated. We supposed that the positive charge (Arg36) in this loop of α-cobratoxin may explain its high affinity to GABAAR and here studied α-neurotoxins from African cobra N. melanoleuca venom for their ability to interact with GABAARs and nAChRs. Three α-neurotoxins, close homologues of the known N. melanoleuca long neurotoxins 1 and 2, were isolated and sequenced. Their analysis on Torpedocalifornica and α7 nAChRs, as well as on acetylcholine binding proteins and on several subtypes of GABAARs, showed that all toxins interacted with the GABAAR much weaker than with the nAChR: one neurotoxin was almost as active as α-cobratoxin, while others manifested lower activity. The earlier hypothesis about the essential role of Arg36 as the determinant of high affinity to GABAAR was not confirmed, but the results obtained suggest that the toxin loop III may contribute to the efficient interaction of some long-chain neurotoxins with GABAAR. One of isolated toxins manifested different affinity to two binding sites on Torpedo nAChR.

scholarly journals Mutation of the high affinity calcium binding sites in cardiac troponin C.

1992 ◽  
Vol 267 (2) ◽  
pp. 825-831 ◽  
Author(s):  
J C Negele ◽  
D G Dotson ◽  
W Liu ◽  
H L Sweeney ◽  
J A Putkey
Keyword(s):  
Binding Sites ◽  
Calcium Binding ◽  
Cardiac Troponin ◽  
Troponin C ◽  
High Affinity ◽  
Cardiac Troponin C ◽  
Calcium Binding Sites
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