MODULATION OF ANTITHROMBIN III ACTIVITY AND ANTITHROMBIN III-THROMBIN COMPLEXES BINDING TO CULTURED CELLS BY MONOCLONAL ANTIBODIES AGAINST ANTITHROMBIN III

1987 ◽  
Author(s):  
S Knoller ◽  
N Savion
Keyword(s):  
Monoclonal Antibodies ◽  
Binding Site ◽  
Conformational Changes ◽  
Antithrombin Iii ◽  
Cultured Cells ◽  
Inhibitory Effect ◽  
National Council ◽  
Corneal Endothelial Cells ◽  
Inhibitory Effects ◽  
Antithrombin Iii Activity

Two monoclonal antibodies (mAb's) against antithrombin III (ATIII) were characterized with respect to their ability to interfere with ATIII activity. AT III activity was measured by its ability to inhibit the amidolitic activity of thrombin on the substrate BCP-100. Incubation of 150 ng of ATIII with 28pg mAb A36R2 prior to addition of 50 ng thrombin totally abolishes the inhibitory effect of ATIII on thrombin. Incubation of 200ng of ATIII with 10 μg of mAb B26R4 prior to addition of 75 ng thrombin raises the inhibitory effects of ATIII from 37% to 100%. We examined the effect of these mAb's on binding of antithrombin III-thrombin (ATIII-Th) complexes to bovine corneal endothelial cells. 120 pg/ml mAb's are reacted with 2 μg/ml ATIII-Th complexes prior to their addition to the cells. mAb A36R2 completely blocks ATIII-Th complexes binding. In contrast, mAb B26R4 enhances binding up to 250% of the control binding.We conclude that mAb A36R2 prevents binding of thrombin to ATIII by recognizing an epitope on ATIII close to thrombin binding site or that its binding to ATIII induces a conformational change in the thrombin binding site thus it no longer recognizes thrombin. mAb B26R4 has a heparin-like effect on ATIII: Its binding to ATIII induces conformational changes which improve thrombin binding to ATIII. There is a correlation between inhibition and enhancement of thrombin binding to ATIII and of ATIII-Th complexes binding to cells by the two mAb's. These mAb's may provide a new tool to control the activity of ATIII and to identify the cellular binding site on the ATIII-Th complex.This research was supported by a grant from the National Council for Research and Development, Israel and G.S.F. München, Germany.

scholarly journals Monoclonal antibodies identify residues 199–216 of the integrin α2 vWFA domain as a functionally important region within α2β1

2000 ◽  
Vol 350 (2) ◽  
pp. 485-493 ◽  
Author(s):  
Danny S. TUCKWELL ◽  
Lyndsay SMITH ◽  
Michelle KORDA ◽  
Janet A. ASKARI ◽  
Sentot SANTOSO ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Binding Site ◽  
Conformational Changes ◽  
Cation Binding ◽  
Inhibitory Antibody ◽  
Collagen Binding ◽  
Collagen Peptide ◽  
Binding Residue ◽  
Important Region ◽  
Domain Mapping

Integrin α2β1 is the major receptor for collagens in the human body, and the collagen-binding site on the α2 subunit von Willebrand factor A-type domain (vWFA domain) is now well defined. However, the biologically important conformational changes that are associated with collagen binding, and the means by which the vWFA domain is integrated into the whole integrin are not completely understood. We have raised monoclonal antibodies against recombinant α2 vWFA domain for use as probes of function. Three antibodies, JA202, JA215 and JA218, inhibited binding to collagen, collagen I C-propeptide and E-cadherin, demonstrating that their function is important for structurally diverse α2β1 ligands. Cross-blocking studies grouped the epitopes into two clusters: (I) JA202, the inhibitory antibody, Gi9, and a non-inhibitory antibody, JA208; (II) JA215 and JA218. Both clusters were sensitive to events at the collagen binding site, as binding of Gi9, JA202, JA215 and JA218 were inhibited by collagen peptide, JA208 binding was enhanced by collagen peptide, and binding of JA202 was decreased after mutagenesis of the cation-binding residue Thr221 to alanine. Binding of cluster I antibodies was inhibited by the anti-functional anti-β1 antibody Mab13, and binding of Gi9 and JA218 to α2β1 was inhibited by substituting Mn2+ for Mg2+, demonstrating that these antibodies were sensitive to changes initiated outside the vWFA domain. Mapping of epitopes showed that JA202 and Gi9 bound between residues 212–216, while JA208 bound between residues 199–216. We have therefore identified two epitope clusters with novel properties; i.e. they are intimately associated with the collagen-binding site, responsive to conformational changes at the collagen-binding site and sensitive to events initiated outside the vWFA domain.

scholarly journals Identification of a 521-Kilodalton Protein (Gli521) Involved in Force Generation or Force Transmission for Mycoplasma mobile Gliding

2005 ◽  
Vol 187 (10) ◽  
pp. 3502-3510 ◽  
Author(s):  
Shintaro Seto ◽  
Atsuko Uenoyama ◽  
Makoto Miyata
Keyword(s):  
Monoclonal Antibodies ◽  
Amino Acid ◽  
Conformational Changes ◽  
Peptide Bond ◽  
Gliding Motility ◽  
Force Generation ◽  
Mycoplasma Species ◽  
Membrane Protrusion ◽  
Force Transmission ◽  
Inhibitory Effects

ABSTRACT Several mycoplasma species are known to glide on solid surfaces such as glass in the direction of the membrane protrusion, but the mechanism underlying this movement is unknown. To identify a novel protein involved in gliding, we raised monoclonal antibodies against a detergent-insoluble protein fraction of Mycoplasma mobile, the fastest glider, and screened the antibodies for inhibitory effects on gliding. Five monoclonal antibodies stopped the movement of gliding mycoplasmas, keeping them on the glass surface, and all of them recognized a large protein in immunoblotting. This protein, named Gli521, is composed of 4,738 amino acids, has a predicted molecular mass of 520,559 Da, and is coded downstream of a gene for another gliding protein, Gli349, which is known to be responsible for glass binding during gliding. Edman degradation analysis indicated that the N-terminal region is processed at the peptide bond between the amino acid residues at positions 43 and 44. Analysis of gliding mutants isolated previously revealed that the Gli521 protein is missing in a nonbinding mutant, m9, where the gli521 gene is truncated by a nonsense mutation at the codon for the amino acid at position 1170. Immunofluorescence and immunoelectron microscopy indicated that Gli521 localizes all around the base of the membrane protrusion, at the “neck,” as previously observed for Gli349. Analysis of the inhibitory effects of the anti-Gli521 antibody on gliding motility revealed that this protein is responsible for force generation or force transmission, a role distinct from that of Gli349, and also suggested conformational changes of Gli349 and Gli521 during gliding.

scholarly journals Significance of RGD Loop and C-Terminal Domain of Echistatin for Recognition of αIIbβ3 and αvβ3 Integrins and Expression of Ligand-Induced Binding Site

Blood ◽  
1997 ◽  
Vol 90 (4) ◽  
pp. 1565-1575 ◽  
Author(s):  
Cezary Marcinkiewicz ◽  
Senadhi Vijay-Kumar ◽  
Mary Ann McLane ◽  
Stefan Niewiarowski
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Inhibitory Effect ◽  
Selective Recognition ◽  
Αvβ3 Integrin ◽  
Inhibit Platelet Aggregation ◽  
Disulfide Bridges ◽  
Terminal Domain ◽  
Αvβ3 Integrins ◽  
Terminal Amino

Abstract Echistatin is a viper venom disintegrin containing RGD loop maintained by disulfide bridges. It binds with a high affinity to αvβ3 and αIIbβ3 and it induces extensive conformational changes in these integrins resulting in expression of ligand-induced binding site (LIBS) epitopes. We investigated the activities of echistatin and its three analogues (R24A, D27W, echistatin 1-41). R24A echistatin did not react with αIIbβ3 and αvβ3 integrins and did not cause LIBS effect. D27W echistatin showed increased binding to αIIbβ3 and decreased binding to αvβ3. This substitution impaired the ability of echistatin to induce LIBS in αvβ3 integrin. Deletion of nine C-terminal amino acids of echistatin decreased its ability to bind αIIbβ3 and inhibit platelet aggregation. Truncated echistatin failed to induce LIBS epitopes on cells transfected with αIIbβ3 and αvβ3 genes. The ability of echistatin 1-41 to compete with binding of vitronectin to immobilized αvβ3 and monoclonal antibody 7E3 to platelets and to VNRC3 cells was decreased, although this analogue, after immobilization, retained its ability to bind purified αvβ3. We propose a hypothesis in which echistatin's RGD loop determines selective recognition of αIIbβ3 and αvβ3 integrin, whereas the C-terminal domain supports its binding to resting integrin and significantly contributes to the expression of LIBS epitope and to conformational changes of the receptor, leading to a further increase of the binding affinity of echistatin and of the inhibitory effect.

scholarly journals Monoclonal antibodies against plasma protease inhibitors: production and characterization of 15 monoclonal antibodies against human antithrombin III. Relation between antigenic determinants and functional sites of antithrombin III

Blood ◽  
1985 ◽  
Vol 65 (5) ◽  
pp. 1201-1207 ◽  
Author(s):  
P Herion ◽  
M Francotte ◽  
D Siberdt ◽  
GG Soto ◽  
J Urbain ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Antithrombin Iii ◽  
Antigenic Determinants ◽  
Mouse Strains ◽  
High Avidity ◽  
Functional Sites ◽  
Crude Preparation ◽  
Alpha 1 Antitrypsin ◽  
Antithrombin Iii Activity

Abstract Fifteen hybridomas secreting monoclonal antibodies against human antithrombin III, originating from two mouse strains, have been produced by the cell fusion technique. Eight monoclonal antibodies belong to the class IgG1, five to the class IgG2a, and two to the class IgG2b. All light chains belong to the kappa group. No cross-reaction of the monoclonal antibodies have been observed with a crude preparation of albumin nor with alpha 1-antitrypsin and alpha 2-antiplasmin. Five of these monoclonal antibodies exhibit a relatively high avidity for antithrombin III. Inhibition experiments showed that the 15 monoclonal antibodies define seven more or less independent antigenic regions on the antithrombin III molecule. Examination of the effects of these antibodies on the inhibitory capacity of antithrombin III toward thrombin activity, either in the presence or in the absence of heparin, showed that several monoclonal antibodies inhibit the antithrombin III activity and allowed to relate some of the antigenic determinants to functional sites on the antithrombin III molecule.

scholarly journals Nanobody mediated neutralization reveals an Achilles heel for norovirus

2020 ◽  
Author(s):  
Anna D. Koromyslova ◽  
Jessica Michelle Devant ◽  
Turgay Kilic ◽  
Charles D. Sabin ◽  
Virginie Malak ◽  
...  
Keyword(s):  
Cell Culture ◽  
Binding Site ◽  
Receptor Binding ◽  
Conformational Changes ◽  
Structural Modification ◽  
Cultured Cells ◽  
Murine Norovirus ◽  
Human Norovirus ◽  
Receptor Binding Site ◽  
P Domain

ABSTRACTHuman norovirus frequently causes outbreaks of acute gastroenteritis. Although discovered more than five decades ago, antiviral development has, until recently, been hampered by the lack of a reliable human norovirus cell culture system. Nevertheless, a lot of pathogenesis studies were accomplished using murine norovirus (MNV), which can be grown routinely in cell culture. In this study, we analysed a sizeable library of Nanobodies that were raised against the murine norovirus virion with the main purpose of developing Nanobody-based inhibitors. We discovered two types of neutralizing Nanobodies and analysed the inhibition mechanisms using X-ray crystallography, cryo-EM, and cell culture techniques. The first type bound on the top region of the protruding (P) domain. Interestingly, the Nanobody binding region closely overlapped the MNV receptor-binding site and collectively shared numerous P domain-binding residues. In addition, we showed that these Nanobodies competed with the soluble receptor and this action blocked virion attachment to cultured cells. The second type bound at a dimeric interface on the lower side of the P dimer. We discovered that these Nanobodies disrupted a structural change in the capsid associated with binding co-factors (i.e., metal cations/bile acid). Indeed, we found that capsids underwent major conformational changes following addition of Mg2+ or Ca2+. Ultimately, these Nanobodies directly obstructed a structural modification reserved for a post-receptor attachment stage. Altogether, our new data show that Nanobody-based inhibition could occur by blocking functional and structural capsid properties.AUTHOR SUMMARYThis research discovered and analysed two different types of MNV neutralizing Nanobodies. The top-binding Nanobodies sterically inhibited the receptor-binding site, whereas the dimeric-binding Nanobodies interfered with a structural modification associated with co-factor binding. Moreover, we found that the capsid contained a number of vulnerable regions that were essential for viral replication. In fact, the capsid appeared to be organized in a state of flux, which could be important for co-factor/receptor binding functions. Blocking these capsid-binding events with Nanobodies directly inhibited essential capsid functions. Moreover, a number of MNV-specific Nanobody binding epitopes were comparable to human norovirus-specific Nanobody inhibitors. Therefore, this additional structural and inhibition information could be further exploited in the development of human norovirus antivirals.

scholarly journals Mapping early conformational changes in αIIb and β3 during biogenesis reveals a potential mechanism for αIIbβ3 adopting its bent conformation

Blood ◽  
2007 ◽  
Vol 109 (9) ◽  
pp. 3725-3732 ◽  
Author(s):  
W. Beau Mitchell ◽  
Jihong Li ◽  
Marta Murcia ◽  
Nathalie Valentin ◽  
Peter J. Newman ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Complex Formation ◽  
Binding Site ◽  
Conformational Changes ◽  
Current Evidence ◽  
Potential Mechanism ◽  
Integrin Αiibβ3 ◽  
Working Model ◽  
Control Complex ◽  
Specific Ligand

Abstract Current evidence supports a model in which the low-affinity state of the platelet integrin αIIbβ3 results from αIIbβ3 adopting a bent conformation. To assess αIIbβ3 biogenesis and how αIIbβ3 initially adopts the bent conformation, we mapped the conformational states occupied by αIIb and β3 during biogenesis using conformation-specific monoclonal antibodies (mAbs). We found that αIIbβ3 complex formation was not limited by the availability of either free pro-αIIb or free β3, suggesting that other molecules, perhaps chaperones, control complex formation. Five β3-specific, ligand-induced binding site (LIBS) mAbs reacted with much or all free β3 but not with β3 when in complex with mature αIIb, suggesting that β3 adopts its mature conformation only after complex formation. Conversely, 2 αIIb-specific LIBS mAbs directed against the αIIb Calf-2 region adjacent to the membrane reacted with only minor fractions of free pro-αIIb, raising the possibility that pro-αIIb adopts a bent conformation early in biogenesis. Our data suggest a working model in which pro-αIIb adopts a bent conformation soon after synthesis, and then β3 assumes its bent conformation by virtue of its interaction with the bent pro-αIIb.

scholarly journals Monoclonal antibodies against plasma protease inhibitors: production and characterization of 15 monoclonal antibodies against human antithrombin III. Relation between antigenic determinants and functional sites of antithrombin III

Blood ◽  
1985 ◽  
Vol 65 (5) ◽  
pp. 1201-1207
Author(s):  
P Herion ◽  
M Francotte ◽  
D Siberdt ◽  
GG Soto ◽  
J Urbain ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Antithrombin Iii ◽  
Antigenic Determinants ◽  
Mouse Strains ◽  
High Avidity ◽  
Functional Sites ◽  
Crude Preparation ◽  
Alpha 1 Antitrypsin ◽  
Antithrombin Iii Activity

Fifteen hybridomas secreting monoclonal antibodies against human antithrombin III, originating from two mouse strains, have been produced by the cell fusion technique. Eight monoclonal antibodies belong to the class IgG1, five to the class IgG2a, and two to the class IgG2b. All light chains belong to the kappa group. No cross-reaction of the monoclonal antibodies have been observed with a crude preparation of albumin nor with alpha 1-antitrypsin and alpha 2-antiplasmin. Five of these monoclonal antibodies exhibit a relatively high avidity for antithrombin III. Inhibition experiments showed that the 15 monoclonal antibodies define seven more or less independent antigenic regions on the antithrombin III molecule. Examination of the effects of these antibodies on the inhibitory capacity of antithrombin III toward thrombin activity, either in the presence or in the absence of heparin, showed that several monoclonal antibodies inhibit the antithrombin III activity and allowed to relate some of the antigenic determinants to functional sites on the antithrombin III molecule.

scholarly journals Significance of RGD Loop and C-Terminal Domain of Echistatin for Recognition of αIIbβ3 and αvβ3 Integrins and Expression of Ligand-Induced Binding Site

Blood ◽  
1997 ◽  
Vol 90 (4) ◽  
pp. 1565-1575 ◽  
Author(s):  
Cezary Marcinkiewicz ◽  
Senadhi Vijay-Kumar ◽  
Mary Ann McLane ◽  
Stefan Niewiarowski
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Inhibitory Effect ◽  
Selective Recognition ◽  
Αvβ3 Integrin ◽  
Inhibit Platelet Aggregation ◽  
Disulfide Bridges ◽  
Terminal Domain ◽  
Αvβ3 Integrins ◽  
Terminal Amino

Echistatin is a viper venom disintegrin containing RGD loop maintained by disulfide bridges. It binds with a high affinity to αvβ3 and αIIbβ3 and it induces extensive conformational changes in these integrins resulting in expression of ligand-induced binding site (LIBS) epitopes. We investigated the activities of echistatin and its three analogues (R24A, D27W, echistatin 1-41). R24A echistatin did not react with αIIbβ3 and αvβ3 integrins and did not cause LIBS effect. D27W echistatin showed increased binding to αIIbβ3 and decreased binding to αvβ3. This substitution impaired the ability of echistatin to induce LIBS in αvβ3 integrin. Deletion of nine C-terminal amino acids of echistatin decreased its ability to bind αIIbβ3 and inhibit platelet aggregation. Truncated echistatin failed to induce LIBS epitopes on cells transfected with αIIbβ3 and αvβ3 genes. The ability of echistatin 1-41 to compete with binding of vitronectin to immobilized αvβ3 and monoclonal antibody 7E3 to platelets and to VNRC3 cells was decreased, although this analogue, after immobilization, retained its ability to bind purified αvβ3. We propose a hypothesis in which echistatin's RGD loop determines selective recognition of αIIbβ3 and αvβ3 integrin, whereas the C-terminal domain supports its binding to resting integrin and significantly contributes to the expression of LIBS epitope and to conformational changes of the receptor, leading to a further increase of the binding affinity of echistatin and of the inhibitory effect.

scholarly journals Targeting the autolysis loop of urokinase-type plasminogen activator with conformation-specific monoclonal antibodies

2011 ◽  
Vol 438 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Kenneth A. Botkjaer ◽  
Sarah Fogh ◽  
Erin C. Bekes ◽  
Zhuo Chen ◽  
Grant E. Blouse ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Plasminogen Activator ◽  
Conformational Changes ◽  
Active Site ◽  
Protease Activity ◽  
Cultured Cells ◽  
Model Systems ◽  
Zymogen Activation ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

Tight regulation of serine proteases is essential for their physiological function, and unbalanced states of protease activity have been implicated in a variety of human diseases. One key example is the presence of uPA (urokinase-type plasminogen activator) in different human cancer types, with high levels correlating with a poor prognosis. This observation has stimulated efforts into finding new principles for intervening with uPA's activity. In the present study we characterize the so-called autolysis loop in the catalytic domain of uPA as a potential inhibitory target. This loop was found to harbour the epitopes for three conformation-specific monoclonal antibodies, two with a preference for the zymogen form pro-uPA, and one with a preference for active uPA. All three antibodies were shown to have overlapping epitopes, with three common residues being crucial for all three antibodies, demonstrating a direct link between conformational changes of the autolysis loop and the creation of a catalytically mature active site. All three antibodies are potent inhibitors of uPA activity, the two pro-uPA-specific ones by inhibiting conversion of pro-uPA to active uPA and the active uPA-specific antibody by shielding the access of plasminogen to the active site. Furthermore, using immunofluorescence, the conformation-specific antibodies mAb-112 and mAb-12E6B10 enabled us to selectively stain pro-uPA or active uPA on the surface of cultured cells. Moreover, in various independent model systems, the antibodies inhibited tumour cell invasion and dissemination, providing evidence for the feasibility of pharmaceutical intervention with serine protease activity by targeting surface loops that undergo conformational changes during zymogen activation.

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