scholarly journals Site-specific inhibition of myosin-mediated motility in vitro by monoclonal antibodies.

1985 ◽  
Vol 100 (4) ◽  
pp. 1024-1030 ◽  
Author(s):  
P F Flicker ◽  
G Peltz ◽  
M P Sheetz ◽  
P Parham ◽  
J A Spudich
Keyword(s):  
Electron Microscopy ◽  
Monoclonal Antibodies ◽  
Binding Sites ◽  
Functional Assay ◽  
Specific Inhibition ◽  
Myosin Molecule ◽  
Site Specific ◽  
Dictyostelium Myosin ◽  
Cell Biol

Monoclonal antibodies directed against seven different sites on Dictyostelium myosin (Peltz, G., J. A. Spudich, and P. Parham, 1985, J. Cell Biol., 100: 1016-1023) were tested for their ability to inhibit movement of myosin in vitro, using the Nitella-based myosin-mediated bead movement assay (Sheetz, M. P., R. Chasan, and J. A. Spudich, 1984, J. Cell Biol., 99: 1867-1871). To complement this functional assay, we located the binding sites of these antibodies by electron microscopy, using the rotary shadowing technique. One antibody bound to the 18,000-dalton light chain and inhibited movement completely. All of the remaining antibodies bound to various positions along the rod portion of the myosin molecule, which is approximately 1,800 A long. Antibodies that bound to the rod about 470, 680, and 1400 A from the head-tail junction did not alter myosin movement. One antibody appeared to bind very close to the head-tail junction and to inhibit movement 50%. Surprisingly, three antibodies that bound about 1,200 A from the head-tail junction inhibited movement completely. This inhibition did not depend on using intact IgG, since Fab' fragments had the same effect.

scholarly journals Monoclonal antibodies against seven sites on the head and tail of Dictyostelium myosin.

1985 ◽  
Vol 100 (4) ◽  
pp. 1016-1023 ◽  
Author(s):  
G Peltz ◽  
J A Spudich ◽  
P Parham
Keyword(s):  
Monoclonal Antibodies ◽  
Atpase Activity ◽  
Heavy Chain ◽  
Light Chain ◽  
Binding Sites ◽  
Myosin Molecule ◽  
Dictyostelium Myosin ◽  
Antigenic Sites ◽  
Myosin Filaments ◽  
A Site

Ten monoclonal antibodies (My1-10) against Dictyostelium discoideum myosin were prepared and characterized. Nine bound to the 210-kD heavy chain and one (My8) bound to the 18-kD light chain. They defined six topographically distinct antigenic sites of the heavy chain. Five binding sites (the My1, My5, My10 site, and the My2, My3, My4, and My9 sites) are located on the rod portion of the myosin molecule. The position of the sixth site (the My6 and My7 site) is less certain, but it appears to be near the junction of the globular heads and the rod. Three of the antibodies (My2, My3, and My6) bound to myosin filaments in solution and could be sedimented in stoichiometric amounts with the filamentous myosin. In contrast, My4, which recognized a site on the rod, inhibited the polymerization of monomeric myosin into filaments. A single antibody (My6) affected the actin-activated ATPase of myosin. The nature of the effect depended on the valency of the antibody and the myosin. Bivalent IgG and F(ab')2 fragments of My6 inhibited the actin-activated ATPase of filamentous myosin by 50% whereas univalent Fab' fragments increased the activity by 50%. The actin-activated ATPase activity of the soluble chymotryptic fragment of myosin was increased 80-90% by both F(ab')2 and Fab' of My6.

scholarly journals Probing the Flavivirus Membrane Fusion Mechanism by Using Monoclonal Antibodies

2007 ◽  
Vol 81 (20) ◽  
pp. 11526-11531 ◽  
Author(s):  
Karin Stiasny ◽  
Samantha Brandler ◽  
Christian Kössl ◽  
Franz X. Heinz
Keyword(s):  
Monoclonal Antibodies ◽  
Fusion Protein ◽  
Binding Sites ◽  
Fusion Inhibition ◽  
Tick Borne Encephalitis ◽  
Target Membrane ◽  
Initial Interaction ◽  
Tick Borne Encephalitis Virus ◽  
Late Stages

ABSTRACT In this study, we investigated in a flavivirus model (tick-borne encephalitis virus) the mechanisms of fusion inhibition by monoclonal antibodies directed to the different domains of the fusion protein (E) and to different sites within each of the domains by using in vitro fusion assays. Our data indicate that, depending on the location of their binding sites, the monoclonal antibodies impaired early or late stages of the fusion process, by blocking the initial interaction with the target membrane or by interfering with the proper formation of the postfusion structure of E, respectively. These data provide new insights into the mechanisms of flavivirus fusion inhibition by antibodies and their possible contribution to virus neutralization.

Site-specific DNA binding of nuclear factor I: analyses of cellular binding sites

1985 ◽  
Vol 5 (5) ◽  
pp. 964-971
Author(s):  
R M Gronostajski ◽  
S Adhya ◽  
K Nagata ◽  
R A Guggenheimer ◽  
J Hurwitz
Keyword(s):  
Dna Binding ◽  
Hela Cell ◽  
Dna Sequences ◽  
Binding Sites ◽  
Consensus Sequence ◽  
Nuclear Factor ◽  
Site Specific ◽  
Factor I ◽  
Nuclear Factor I

Nuclear factor I is a cellular site-specific DNA-binding protein required for the efficient in vitro replication of adenovirus DNA. We have characterized human DNA sequences to which nuclear factor I binds. Three nuclear factor I binding sites (FIB sites), isolated from HeLa cell DNA, each contain the sequence TGG(N)6-7GCCAA. Comparison with other known and putative FIB sites suggests that this sequence is important for the binding of nuclear factor I. Nuclear factor I protects a 25- to 30-base-pair region surrounding this sequence from digestion by DNase I. Methylation protection studies suggest that nuclear factor I interacts with guanine residues within the TGG(N)6-7GCCAA consensus sequence. One binding site (FIB-2) contained a restriction endonuclease HaeIII cleavage site (GGCC) at the 5' end of the GCCAA motif. Digestion of FIB-2 with HaeIII abolished the binding of nuclear factor I. Southern blot analyses indicate that the cellular FIB sites described here are present within single-copy DNA in the HeLa cell genome.

scholarly journals A comparison of HER2 tumor accumulations of Ga-67 labeled anti-HER2 antibody with chemically and site-specifically conjugated bifunctional chelators

2020 ◽  
Author(s):  
Yumiko Kono ◽  
Keita Utsunomiya ◽  
Yuta Ohira ◽  
Hirokazu Satoh ◽  
Naoki Kan ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Binding Capacity ◽  
Binding Activity ◽  
Pharmacokinetic Analysis ◽  
Pharmacokinetic Studies ◽  
Her2 Positive ◽  
Site Specific ◽  
Planar Images

Abstract Background Monoclonal antibodies (mAb) developed to target specific cancers have achieved considerable success to-date. To further enhance therapeutic efficacy monoclonal antibodies may be conjugated with a cytotoxic drug or radioisotope. We present the development of new method based on site-specific conjugation (SSC) for targeting HER2. The study design involves a comparison of the accumulation of Ga-67 labeled anti-HER2 antibodies with SSC versus conventional chemical conjugation in HER2-positive tumors. Anti-HER2 antibodies were chemically conjugated (Chem) with the bifunctional chelator deferoxamine (Chem-mAb). The resulting chemical conjugate was radiolabeled with Ga-67 yielding Ga-67-Chem -mAb. The SSC anti-HER2 antibodies enzymatically conjugated with deferoxamine using transglutaminase (SSC-mAb) and radiolabeled with Ga-67 yielding Ga-67-SSC-mAb. In vitro, the binding activity of HER2 to both conjugated antibodies was measured using surface Plasmon resonance. In vivo, a xenograft mouse model consisting of transplanted CHO/HER2 were divided into two groups, the Chem and the SSC group. Planar images were acquired over three days after each mAb injection, respectively. Pharmacokinetic analysis was used to compare the Chem group to the SSC group, for Ga-67 accumulation. Result The SSC and Chem groups were found to have similar HER2 binding capacity, however the tumor accumulation ratio gradually increased in the SSC group. The pharmacokinetic studies also found that radiolabeled mAb accumulation was significantly higher in the SSC group than the Chem group in not only the tumors, but also in blood and in other organs. Conclusion The new site-specific conjugation may improve targeted antigen-specific cancer radioimmunotherapy and may, due to higher retention, require a lower dose.

scholarly journals EBs clip CLIPs to growing microtubule ends

2008 ◽  
Vol 183 (7) ◽  
pp. 1183-1185 ◽  
Author(s):  
Torsten Wittmann
Keyword(s):  
Exponential Decay ◽  
Binding Sites ◽  
Biochemical Property ◽  
Cell Biol ◽  
The Subject

Proteins that track growing microtubule (MT) ends are important for many aspects of intracellular MT function, but the mechanism by which these +TIPs accumulate at MT ends has been the subject of a long-standing controversy. In this issue, Bieling et al. (Bieling, P., S. Kandels-Lewis, I.A. Telley, J. van Dijk, C. Janke, and T. Surrey. 2008. J. Cell Biol. 183:1223–1233) reconstitute plus end tracking of EB1 and CLIP-170 in vitro, which demonstrates that CLIP-170 plus end tracking is EB1-dependent and that both +TIPs rapidly exchange between a soluble and a plus end–associated pool. This strongly supports the hypothesis that plus end tracking depends on a biochemical property of growing MT ends, and that the characteristic +TIP comets result from the generation of new +TIP binding sites through MT polymerization in combination with the exponential decay of these binding sites.

Immunolocalization and characterization of the low molecular weight antigen (4–5 kDa) ofToxoplasma gondiithat elicits an early IgM response upon primary infection

Parasitology ◽  
1994 ◽  
Vol 108 (2) ◽  
pp. 139-145 ◽  
Author(s):  
S. Tomavo ◽  
G. Couvreur ◽  
M. A. Leriche ◽  
A. Sadak ◽  
A. Achbarou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Monoclonal Antibodies ◽  
Primary Infection ◽  
Low Molecular Weight ◽  
Immuno Electron Microscopy ◽  
Surface Localization

SUMMARYA striking feature of toxoplasmic seroconversion is the prominent and early IgM response to a low molecular weight antigen of 4–5 kDa. Two different monoclonal antibodies directed against the 4–5 kDa antigen have been generated and used to characterize this molecule. Using these monoclonal antibodies, we could demonstrate the surface localization of the lowMrantigen by immunofluorescence and immuno-electron microscopy assays. By immunoblotting, we observed that one of the monoclonal antibodies was unable to recognize the 4–5 kDa antigen in tachyzoites propagated in cell culture, indicating an epitope variability betweenToxoplasma gondiitachyzoites grownin vivoandin vitro. We discuss the implications of this latter finding in the design of diagnostic reagents.

scholarly journals Human platelet myosin. II. In vitro assembly and structure of myosin filaments.

1975 ◽  
Vol 67 (1) ◽  
pp. 72-92 ◽  
Author(s):  
R Niederman ◽  
T D Pollard
Keyword(s):  
Electron Microscopy ◽  
Ionic Strength ◽  
Thin Section ◽  
Human Platelet ◽  
Myosin Ii ◽  
Myosin Molecule ◽  
Myosin Filaments ◽  
In Vitro Assembly ◽  
Myosin Rod

We have used electron microscopy and solubility measurements to investigate the assembly and structure of purified human platelet myosin and myosin rod into filaments. In buffers with ionic strengths of less than 0.3 M, platelet myosin forms filaments which are remarkable for their small size, being only 320 nm long and 10-11 nm wide in the center of the bare zone. The dimensions of these filaments are not affected greatly by variation of the pH between 7 and 8, variation of the ionic strength between 0.05 and 0.2 M, the presence or absence of 1 mM Mg++ or ATP, or variation of the myosin concentration between 0.05 and 0.7 mg/ml. In 1 mM Ca++ and at pH 6.5 the filaments grow slightly larger. More than 90% of purified platelet myosin molecules assemble into filaments in 0.1 M KC1 at pH 7. Purified preparations of the tail fragment of platelet myosin also form filaments. These filaments are slightly larger than myosin filaments formed under the same conditions, indicating that the size of the myosin filaments may be influenced by some interaction between the head and tail portions of myosin molecules. Calculations based on the size and shape of the myosin filaments, the dimensions of the myosin molecule and analysis of the bare zone reveal that the synthetic platelet myosin filaments consists of 28 myosin molecules arranged in a bipolar array with the heads of two myosin molecules projecting from the backbone of the filament at 14-15 nm intervals. The heads appear to be loosely attached to the backbone by a flexible portion of the myosin tail. Given the concentration of myosin in platelets and the number of myosin molecules per filament, very few of these thin myosin filaments should be present in a thin section of a platelet, even if all of the myosin molecules are aggregated into filaments.

scholarly journals Mapping of Staphylococcal Enterotoxin A Functional Binding Sites and Presentation by Monoclonal Antibodies and Fusion Proteins

1999 ◽  
Vol 67 (4) ◽  
pp. 1894-1900
Author(s):  
Wahib Mahana
Keyword(s):  
Cell Proliferation ◽  
Monoclonal Antibodies ◽  
T Cell ◽  
Mhc Class Ii ◽  
Binding Sites ◽  
Fusion Proteins ◽  
Biological Activities ◽  
Interleukin 2 ◽  
Class Ii

ABSTRACT Staphylococal enterotoxins (SE) bind with high affinity to major histocompatibility complex (MHC) class II proteins and stimulate large number of T cells via the Vβ region of the T-cell receptor (TCR). To map the epitopes of SE type A (SEA) involved in MHC binding and cell proliferation, 20 specific anti-SEA monoclonal antibodies (MAbs) and two large glutathione S-transferase fusion proteins corresponding to the amino and carboxy termini, respectively, of SEA were used. The functionality of these antibodies was tested, by MHC binding inhibition, interleukin-2 production, and T-cell proliferation assays. Moreover, I studied the ability of the MAbs to present SEA in vitro to human and murine cells and their reactivity with the two fusion proteins. This study showed that all of the MAbs have a defined effect on one or both immunological properties of SEA and were able to present SEA to human and murine cells. However, one MAb (4H8) recognized SEA but without any interference with its biological activities. When the MAbs were tested to react with the two fusion proteins representing the SEA molecule, all of the MAbs were negative except for two. These results confirmed the presence of two functionally different binding sites of SEA with MHC class II molecules and the importance of the disulfide loop for the mitogenic activity of SEA. I further demonstrated that MAbs can present SEA to immune cells independent of the site recognized by the antibody and that the integrity of the SEA molecule is very important for its functions.

scholarly journals Subfractionation of hepatic endosomes in Nycodenz gradients and by free-flow electrophoresis. Separation of ligand-transporting and receptor-enriched membranes

1985 ◽  
Vol 232 (1) ◽  
pp. 25-32 ◽  
Author(s):  
W H Evans ◽  
N Flint
Keyword(s):  
Electron Microscopy ◽  
Alkaline Phosphatase ◽  
Binding Sites ◽  
Average Diameter ◽  
Free Flow ◽  
Density Range ◽  
Short Intervals ◽  
Electrophoresis Separation ◽  
Isopycnic Centrifugation

The complexity of rat liver endosome fractions containing internalized radioiodinated asialotransferrin, asialo-(alkaline phosphatase), insulin and prolactin was investigated by using free-flow electrophoresis and isopycnic centrifugation in Nycodenz gradients. Two subfractions were separated by free-flow electrophoresis. Both subfractions contained receptors for asialoglycoprotein and insulin. Glycosyltransferase activities were associated with the more electronegative vesicles, whereas 5′-nucleotidase and alkaline phosphodiesterase activities were associated with the less electronegative vesicles. Three subfractions were separated on Nycodenz gradients. Two subfractions, previously shown to become acidified in vitro, contained the ligands. At short intervals after uptake (1-2 min), ligands were mainly in subfraction DN-2 (density 1.115 g/cm3), but movement into subfraction DN-1 (density 1.090 g/cm3) had occurred 10-15 min after internalization. Low amounts of glycosyltransferase activities were associated with subfraction DN-2, and 5′-nucleotidase and alkaline phosphodiesterase activities were mainly located in subfraction DN-1. The binding sites for asialoglycoproteins and insulin were distributed towards the higher density range in the Nycodenz gradients, thus indicating a segregation of receptor-enriched vesicles and those vesicles containing the various ligands 10-15 min after internalization. Electron microscopy of the subfractions separated on Nycodenz gradients indicated that whereas the ligand-transporting fractions consisted mainly of empty vesicles (average diameter 100-150 nm), the receptor-enriched component was more granular and smaller (average diameter 70-95 nm). The properties of the endosome subfraction are used to assign their origin to the regions of the endocytic compartment where ligand-receptor dissociation and separation occur.

scholarly journals Structural basis of malaria transmission blockade by a monoclonal antibody to gamete fusogen HAP2

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Juan Feng ◽  
Xianchi Dong ◽  
Adam DeCosta ◽  
Yang Su ◽  
Fiona Angrisano ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Malaria Transmission ◽  
Plasmodium Berghei ◽  
Structural Basis ◽  
Block Transmission ◽  
Mechanism Of Inhibition

HAP2 is a transmembrane gamete fusogen found in multiple eukaryotic kingdoms and is structurally homologous to viral class II fusogens. Studies in Plasmodium have suggested that HAP2 is an attractive target for vaccines that block transmission of malaria. HAP2 has three extracellular domains, arranged in the order D2, D1, and D3. Here, we report monoclonal antibodies against the D3 fragment of Plasmodium berghei HAP2 and crystal structures of D3 in complex with Fab fragments of two of these antibodies, one of which blocks fertilization of Plasmodium berghei in vitro and transmission of malaria in mosquitoes. We also show how this Fab binds the complete HAP2 ectodomain with electron microscopy. The two antibodies cross-react with HAP2 among multiple plasmodial species. Our characterization of the Plasmodium D3 structure, HAP2 ectodomain architecture, and mechanism of inhibition provide insights for the development of a vaccine to block malaria transmission.

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