No abstract

Binding of divalent metal ions to hepatic soluble /]-galactoside binding lectin was studied using electron spin resonance (ESR) spectroscopy. The Mn 2+ bound to hepatic lectin could be displaced by Mg 2+, Cu 2+, Ni 2+ and Ca 2+ but not by Sr 2+. As the ionic radii of Mg 2+ (0.65 A), Cu 2+ (0~73 ~.) and Ni 2+ (0.72 A) are appreciably smaller than Ca 2+ (0.99 A), it appears that the Mn 2+ binding site is more accessible to Mg 2+, Cu 2+, and Ni 2+ as compared to Ca 2+, the ionic radius of Mn 2+ being 0.80 .~,. Sr 2+ with an ionic radius of 1.13 is thus unable to displace bound Mn 2+. Surprisingly, the presence of specific sugars like a-lactose, or a-o-galactose facilitated the displacement of bound Mn 2+ by metal ions whereas non-specific sugars, i.e. a-D-glucose, j~-ofructose and a-D-ribose had no effect. It appears that minor perturbations in the saccharide binding site significantly affect the ability of the metal binding site to ligate bivalent metals.

Peritoneal macrophages from mice and guinea pigs pretreated with Freund's complete adjuvant (FCA) or any other immunostimulant when packed in a glass capillary and placed in a migration chamber migrated to a larger area than macrophages from normal untreated animals. The extent of migration could be correlated with the dose of FCA and the period of treatment. Under optimum conditions the ratio between the areas of migration of macrophages from FCA-treated animals and of macrophages from untreated animals was above 3.0. A close correlation was observed between macrophage migration and delayed type hypersensitivity (DTH) response in animals sensitized with ovalbumin or sheep red blood cells. The macrophages of immunostimulant-treated animals had relatively higher phagocytic activity. The macrophage migration index (MMI) appears to be a close correlate of macrophage activation and possibly also of the status of cell mediated immune response.

Galectin-1 requires a reducing environment for its lectin activity and the carbohydrate binding function is destroyed in oxidizing condition. In this report we provide direct evidence that the oxidation of goat hepatic galectin-1 perturbs its carbohydrate recognition domain and this could be due to changes in secondary structure of goat hepatic galectin-1. Conformational changes in goat hepatic galectin-1 due to oxidation were investigated by absorption, fluorescence and circular dichroism measurements.

The oxidation of erythrocyte membrane has been widely used as a model to study the damage of biomembranes by free radicals. Whether binding of lectin to erythrocytes has any effect on peroxidant injury has never been studied. This study reports for the first time that crosslinking of erythrocyte surface glycoprotein by an exogenous lectin significantly enhances the susceptibility to membrane damage by free radicals, as evidenced by the increase in membrane fluidity measured by EPR using spin label and the increase in the amount of oxyhemoglobin liberated due to cell lysis.