scholarly journals Structure and stability of Ricinus communis haemagglutinin

1986 ◽  
Vol 240 (1) ◽  
pp. 227-231 ◽  
Author(s):  
J P Frénoy ◽  
A T Tran ◽  
R Bourrillon
Keyword(s):  
Light Scattering ◽  
Thermal Denaturation ◽  
Analytical Ultracentrifugation ◽  
Ricinus Communis ◽  
Low Ph ◽  
Molecular Properties ◽  
Native Structure ◽  
Guanidinium Chloride ◽  
Ph Dependent ◽  
Conformation Transition

The molecular properties of the haemagglutinin of Ricinus communis (RCA I or RCA 120) were evaluated by analytical ultracentrifugation, light-scattering, c.d. and fluorescence. The native molecule had a fairly expanded structure (f/f0 = 1.43) and dissociated into two subunits of equal size in 6 M-guanidinium chloride. This native structure was stable in alkali (up to pH 11) and resistant to thermal denaturation at neutrality. A pH-triggered change in the haemagglutinin conformation was observed and characterized by analytical ultracentrifugation, c.d. and fluorescence between pH 7 and 4.5, the range in which its affinity for galactosides decreased [Yamasaki, Absar & Funatsu (1985) Biochim, Biophys. Acta 828, 155-161]. These results are discussed in relation to those reported in the literature for other lectins and more especially ricin, for which a pH-dependent conformation transition has been observed in the same range of low pH.

scholarly journals Effect of physical environment on the conformation of ricin Influence of low pH

1986 ◽  
Vol 240 (1) ◽  
pp. 221-226 ◽  
Author(s):  
J P Frénoy
Keyword(s):  
Physical Environment ◽  
Analytical Ultracentrifugation ◽  
Ricinus Communis ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Sedimentation Coefficient ◽  
Living Cells ◽  
Low Ph ◽  
Molecular Properties ◽  
Physical Conditions

The molecular properties of ricin (the toxic lectin from Ricinus communis seeds, RCA II or RCA 60) were evaluated by analytical ultracentrifugation, viscosimetry, c.d., fluorescence and equilibrium dialysis. Measurements of sedimentation (S0(20,W) = 4.60 S) and viscosity (eta = 2.96 × 10(-2) dl/g) indicated that, at neutral pH, the ricin molecule is very compact. Various transitions were explored, and a pH-triggered change in the ricin conformation was observed between pH 7 and 4. In this range, the sedimentation coefficient, far-u.v. c.d. and fluorescence altered simultaneously without unfolding. Below pH 7 the change in the ricin conformation was accompanied by a decrease in the affinity of ricin for galactosides, and at pH 4.0 by an alteration in its binding capacity. These effects of low pH are discussed in relation to the physical conditions encountered by ricin molecules during their entry into living cells.

pH-dependent Gelation of Gastric Mucin

2005 ◽  
Vol 897 ◽  
Author(s):  
Rama Bansil ◽  
Jonathan Celli ◽  
Benard Chasan ◽  
Shyamsundar Erramilli ◽  
Zhenning Hong ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Low Ph ◽  
Gastric Mucin ◽  
Force Microscopy ◽  
Atomic Force ◽  
Visual Evidence ◽  
Ph Dependent ◽  
Microscopic Dynamic

AbstractWe discuss the mechanism by which gastric mucin forms a gel at low pH, which serves to protect the stomach from being damaged by the acidic gastric juice that it secretes. Frequency dependence of viscoelastic moduli of pig gastric mucin gels obtained by microscopic dynamic light scattering is presented. Atomic Force Microscopy provides direct visual evidence to indicate that mucin broken into its subunits does not gel at low pH.

scholarly journals Functional Entry of Baculovirus into Insect and Mammalian Cells Is Dependent on Clathrin-Mediated Endocytosis

2006 ◽  
Vol 80 (17) ◽  
pp. 8830-8833 ◽  
Author(s):  
Gang Long ◽  
Xiaoyu Pan ◽  
Richard Kormelink ◽  
Just M. Vlak
Keyword(s):  
Electron Microscopy ◽  
Mammalian Cells ◽  
Low Ph ◽  
Coated Pits ◽  
Immuno Electron Microscopy ◽  
Endocytosis Pathway ◽  
Ph Dependent ◽  
Budded Virus

ABSTRACT Entry of the budded virus form of baculoviruses into insect and mammalian cells is generally thought to occur through a low-pH-dependent endocytosis pathway, possibly through clathrin-coated pits. This insight is primarily based on (immuno)electron microscopy studies but requires biochemical support to exclude the use of other pathways. Here, we demonstrate using various inhibitors that functional entry of baculoviruses into insect and mammalian cells is primarily dependent on clathrin-mediated endocytosis. Our results further suggest that caveolae are somehow involved in baculovirus entry in mammalian cells. A caveolar endocytosis inhibitor, genistein, enhances baculovirus transduction in these cells considerably.

Entry of bovine viral diarrhea virus into ovine cells occurs through clathrin-dependent endocytosis and low pH-dependent fusion

2009 ◽  
Vol 46 (5) ◽  
pp. 403-407 ◽  
Author(s):  
Basavaraj Shrishail Mathapati ◽  
Niranjan Mishra ◽  
Katherukamem Rajukumar ◽  
Ram Kumar Nema ◽  
Sthita Pragnya Behera ◽  
...  
Keyword(s):  
Bovine Viral Diarrhea Virus ◽  
Low Ph ◽  
Bovine Viral Diarrhea ◽  
Diarrhea Virus ◽  
Viral Diarrhea ◽  
Ph Dependent ◽  
Viral Diarrhea Virus

scholarly journals Endocytosis of Wingless via a dynamin-independent pathway is necessary for signaling in Drosophila wing discs

2016 ◽  
Vol 113 (45) ◽  
pp. E6993-E7002 ◽  
Author(s):  
Anupama Hemalatha ◽  
Chaitra Prabhakara ◽  
Satyajit Mayor
Keyword(s):  
Signal Transduction ◽  
Wing Disc ◽  
Low Ph ◽  
Endocytic Pathway ◽  
Apical Surface ◽  
Receptor Complexes ◽  
Drosophila Wing ◽  
Wing Discs ◽  
Ph Dependent ◽  
Endocytic Pathways

Endocytosis of ligand-receptor complexes regulates signal transduction during development. In particular, clathrin and dynamin-dependent endocytosis has been well studied in the context of patterning of the Drosophila wing disc, wherein apically secreted Wingless (Wg) encounters its receptor, DFrizzled2 (DFz2), resulting in a distinctive dorso-ventral pattern of signaling outputs. Here, we directly track the endocytosis of Wg and DFz2 in the wing disc and demonstrate that Wg is endocytosed from the apical surface devoid of DFz2 via a dynamin-independent CLIC/GEEC pathway, regulated by Arf1, Garz, and class I PI3K. Subsequently, Wg containing CLIC/GEEC endosomes fuse with DFz2-containing vesicles derived from the clathrin and dynamin-dependent endocytic pathway, which results in a low pH-dependent transfer of Wg to DFz2 within the merged and acidified endosome to initiate Wg signaling. The employment of two distinct endocytic pathways exemplifies a mechanism wherein cells in tissues leverage multiple endocytic pathways to spatially regulate signaling.

scholarly journals The amino acid at position 624 in the glycoprotein of SFTSV (severe fever with thrombocytopenia virus) plays a critical role in low-pH-dependent cell fusion activity

2017 ◽  
Vol 38 (2) ◽  
pp. 89-97 ◽  
Author(s):  
Yoshimi TSUDA ◽  
Manabu IGARASHI ◽  
Ryo ITO ◽  
Sanae NISHIO ◽  
Kenta SHIMIZU ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cell Fusion ◽  
Critical Role ◽  
Low Ph ◽  
Dependent Cell ◽  
Ph Dependent ◽  
Severe Fever

scholarly journals The mechanism of assembly of Acanthamoeba myosin-II minifilaments: minifilaments assemble by three successive dimerization steps.

1989 ◽  
Vol 109 (4) ◽  
pp. 1537-1547 ◽  
Author(s):  
J H Sinard ◽  
W F Stafford ◽  
T D Pollard
Keyword(s):  
Electron Microscopy ◽  
Light Scattering ◽  
Ionic Strength ◽  
Analytical Ultracentrifugation ◽  
Myosin Ii ◽  
Alkaline Ph ◽  
Predominant Species ◽  
Assembly Mechanism ◽  
Rapid Equilibrium ◽  
Low Ionic Strength

We used 90 degrees light scattering, analytical ultracentrifugation, and electron microscopy to deduce that Acanthamoeba myosin-II minifilaments, composed of eight molecules each, assemble by a novel mechanism consisting of three successive dimerization steps rather than by the addition of monomers or parallel dimers to a nucleus. Above 200 mM KCl, Acanthamoeba myosin-II is monomeric. At low ionic strength (less than 100 mM KCl), myosin-II polymerizes into bipolar minifilaments. Between 100 and 200 mM KCl, plots of light scattering vs. myosin concentration all extrapolate to the origin but have slopes which decrease with increasing KCl. This indicates that structures intermediate in size between monomers and full length minifilaments are formed, and that the critical concentrations for assembly of these structures is very low. Analytical ultracentrifugation has confirmed that intermediate structures exist at these salt concentrations, and that they are in rapid equilibrium with each other. We believe these structures represent assembly intermediates and have used equilibrium analytical ultracentrifugation and electron microscopy to identify them. Polymerization begins with the formation of antiparallel dimers, with the two tails overlapping by approximately 15 nm. Two antiparallel dimers then associated with a 15-nm stagger to form an antiparallel tetramer. Finally, two tetramers associate with a 30-nm stagger to form the completed minifilament. At very low ionic strengths, the last step in the assembly mechanism is largely reversed and antiparallel tetramers are the predominant species. Alkaline pH, which can also induce minifilament disassembly, produces the same assembly intermediates as are found for salt induced disassembly.

Sign in / Sign up

Export Citation Format

Share Document