The specificity of the binding site of AchatininH, a sialic acid-binding lectin from Achatina fulica

1995 ◽  
Vol 268 (1) ◽  
pp. 115-125 ◽  
Author(s):  
Goutam Sen ◽  
Chitra Mandal
Keyword(s):  
Sialic Acid ◽  
Binding Site ◽  
Achatina Fulica ◽  
Sialic Acid Binding ◽  
Binding Lectin

scholarly journals Chemical-modification studies of a unique sialic acid-binding lectin from the snail Achatina fulica. Involvement of tryptophan and histidine residues in biological activity

1988 ◽  
Vol 254 (1) ◽  
pp. 195-202 ◽  
Author(s):  
S Basu ◽  
C Mandal ◽  
A K Allen
Keyword(s):  
Biological Activity ◽  
Sialic Acid ◽  
Amino Acid ◽  
Fluorescence Emission ◽  
Amino Acid Residues ◽  
Achatina Fulica ◽  
Histidine Residues ◽  
Sialic Acid Binding ◽  
Arginine Residues ◽  
Binding Lectin

A unique sialic acid-binding lectin, achatininH (ATNH) was purified in single step from the haemolymph of the snail Achatina fulica by affinity chromatography on sheep submaxillary-gland mucin coupled to Sepharose 4B. The homogeneity was checked by alkaline gel electrophoresis, immunodiffusion and immunoelectrophoresis. Amino acid analysis showed that the lectin has a fairly high content of acidic amino acid residues (22% of the total). About 1.3% of the residues are half-cystine. The glycoprotein contains 21% carbohydrate. The unusually high content of xylose (6%) and fucose (2.7%) in this snail lectin is quite interesting. The protein was subjected to various chemical modifications in order to detect the amino acid residues and carbohydrate residues present in its binding sites. Modification of tyrosine and arginine residues did not affect the binding activity of ATNH; however, modification of tryptophan and histidine residues led to a complete loss of its biological activity. A marked decrease in the fluorescence emission was found as the tryptophan residues of ATNH were modified. The c.d. data showed the presence of an identical type of conformation in the native and modified agglutinin. The modification of lysine and carboxy residues partially diminished the biological activity. The activity was completely lost after a beta-elimination reaction, indicating that the sugars are O-glycosidically linked to the glycoprotein's protein moiety. This result confirms that the carbohydrate moiety also plays an important role in the agglutination property of this lectin.

scholarly journals Neutrophils do not bind to or phagocytize human immune complexes formed with influenza virus

Blood ◽  
1993 ◽  
Vol 82 (5) ◽  
pp. 1639-1646 ◽  
Author(s):  
DR Ratcliffe ◽  
J Michl ◽  
EB Cramer
Keyword(s):  
Influenza Virus ◽  
Sialic Acid ◽  
Epithelial Cells ◽  
Binding Site ◽  
Immune Complexes ◽  
Human Neutrophils ◽  
Sialic Acid Binding ◽  
Infected Cells ◽  
Neutrophil Adherence ◽  
Human Immune

Abstract Neutrophils appear to form the first line of defense against influenza virus, yet it is unclear how these leukocytes recognize influenza- infected cells. While demonstrating that neutrophils adhere specifically to the sialic acid-binding site on the hemagglutinin molecule (HA) on the surface of influenza-infected (WSN[H1N1]) epithelial cells and not to other viral or epithelial cell antigens, it was observed that human neutrophils do not recognize immune complexes formed with influenza virus. Intact antibodies (mouse monoclonal antibodies [MoAbs] IgG1 and IgG2b, human immune heat-inactivated serum [predominantly IgG1], and IgG purified from human immune serum) that block the sialic acid-binding site on HA significantly reduced (> 80%) neutrophil adherence to influenza-infected epithelial cells. Binding and phagocytosis of free influenza virions and neutrophil agglutination by influenza virus were completely prevented by these antibodies. Intact and F(ab')2 fragments of mouse MoAbs to other viral epitopes caused increased neutrophil adherence to infected cells. This binding was eliminated by F(ab'2) fragments of MoAbs against the sialic acid- binding site on HA, but not by saturating amounts of MoAbs, which block the neutrophil Fc receptors. Thus, it appears that human neutrophils show little ability to bind via their Fc receptors to the immune complexes formed with antibody and either influenza-infected epithelial cells or the free virion. These findings are in contrast to the general dogma, and are the first example of antibody opsonization reducing, rather than enhancing, neutrophil binding and phagocytosis of a pathogen.

scholarly journals Porcine Arterivirus Infection of Alveolar Macrophages Is Mediated by Sialic Acid on the Virus

2004 ◽  
Vol 78 (15) ◽  
pp. 8094-8101 ◽  
Author(s):  
Peter L. Delputte ◽  
Hans J. Nauwynck
Keyword(s):  
Sialic Acid ◽  
Alveolar Macrophages ◽  
Sialic Acids ◽  
Respiratory Syndrome Virus ◽  
Specific Monoclonal Antibody ◽  
Neuraminidase Treatment ◽  
Acid Binding Protein ◽  
Sialic Acid Binding ◽  
High Mannose ◽  
Binding Lectin

ABSTRACT Recently, we showed that porcine sialoadhesin (pSn) mediates internalization of the arterivirus porcine reproductive and respiratory syndrome virus (PRRSV) in alveolar macrophages (Vanderheijden et al., J. Virol. 77:8207-8215, 2003). In rodents and humans, sialoadhesin, or Siglec-1, has been described as a macrophage-restricted molecule and to specifically bind sialic acid moieties. In the current study, we investigated whether pSn is a sialic acid binding protein and, whether so, whether this property is important for its function as a PRRSV receptor. Using untreated and neuraminidase-treated sheep erythrocytes, we showed that pSn binds sialic acid. Furthermore, pSn-specific monoclonal antibody 41D3, which blocks PRRSV infection, inhibited this interaction. PRRSV attachment to and infection of porcine alveolar macrophages (PAM) were both shown to be dependent on the presence of sialic acid on the virus: neuraminidase treatment of virus but not of PAM blocked infection and reduced attachment. Enzymatic removal of all N-linked glycans on the virus with N-glycosidase F reduced PRRSV infection, while exclusive removal of nonsialylated N-linked glycans of the high-mannose type with endoglycosidase H had no significant effect. Free sialyllactose and sialic acid containing (neo)glycoproteins reduced infection, while lactose and (neo)glycoproteins devoid of sialic acids had no significant effect. Studies with linkage-specific neuraminidases and lectins indicated that α2-3- and α2-6-linked sialic acids on the virion are important for PRRSV infection of PAM. From these results, we conclude that pSn is a sialic acid binding lectin and that interactions between sialic acid on the PRRS virion and pSn are essential for PRRSV infection of PAM.

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