Further characterization of the cold agglutinin from the snail Achatina fulica

The cold agglutinin from the albumin gland of the snail Achatina fulica was purified to homogeneity by using sheep gastric mucin-Sepharose 4B as affinity column followed by gel filtration on Bio-Gel P-300. The homogeneity was checked by alkaline gel electrophoresis, immunodiffusion and immunoelectrophoresis. The purified cold agglutinin is a glycoprotein of native M2 220,000 consisting of three non-covalently bound subunits of Mr 84,000, 74,000 and 62,000 and having a pI value of 4.5. The predominant amino acids are aspartic acid and glutamic acid (or amides) and serine, which account for 39% of the residues. About 3% of the residues are half-cystine. The lectin is a glycoprotein with about 30.7% carbohydrate, the most abundant sugars being galactose, N-acetylgalactosamine and N-acetylglucosamine. Mannose, xylose and fucose are also present. The inhibition of agglutination of human umbilical-cord erythrocytes by the cold agglutinin is specific for methyl beta-D-galactoside and also for glycolipids present on cord erythrocytes. The c.d. data show only negative ellipticity values in the far-u.v. region for the protein at various concentrations and temperatures and also in the presence of the hapten lactose (at different concentrations), indicating the presence of a random-coil conformation in the agglutinin that varies according to temperature.

Structural Studies on the Galactan from the Albumin Gland of Achatina fulica

The structure of the galactan isolated from the album in gland of Achatina fulica (African giant snail) was investigated by methylation analyses. The molecule is highly branched. The linkages of the exclusively present D-galactose are 1→3 and /or 1→6. From lectin binding studies it was learnt that the 1→3 linkages possess β-configuration. The anomeric configuration of the 1→6 linkage is unknown. A tentative structure of the galactan is proposed.

Histochemical distribution of certain biochemical constituents in the albumin glands of snails.

The presence in situ of the biochemical constituents galactans, proteinase-inhibitors, and erythro-agglutinin anti-A in snail's albumin gland tissues has been demonstrated by histochemical techniques using fluorescein isothiocyanate (FITC)-conjugated counterparts; namely, anti-galactan-specific lectins, different proteinases, and blood group A substance. Invariably, these constituents are localized as globular structures, predominantly within the lobules of the gland tissue. There is a good correlation between the histochemical findings and the previously reported biochemical and serological findings for these substances.

Proteinase-Inhibitors in Albumin Glands of Achatina fulica

Three different polyvalent proteinase-inhibitors have been detected in the albumin gland of the snail, Achatina fulica and identified by means of fibrin-agar immunelectrophoresis. The inhibitory activity of these substances against several proteinases from different sources was investigated.