A sunflower lectin with antipathogenic properties and putative pharmacological applications

MARIANA REGENTE; MARIANGELA DIZ; MARCELA PINEDO; MERCEDES ELIZALDE ; VALDIRENE GOMES; LAURA DE LA CANAL

Mar del Plata

Conferencia; 18th International Sunflower Conference; 2012

ASAGIR

Lectins are carbohydrate-binding proteins with high specificity for a variety of sugar motives in glycoconjugates. This characteristic supports the cell agglutination, antitumoral, immunomodulation, antiviral, antibacterial, antifungal and insecticidal activities associated to certain lectins. Among them, the jacalin-related lectins (JRLs) are considered to be a small sub-family composed of galactose and mannose-specific members. Using a proteomic approach we have detected in sunflower seedlings a 16 kDa protein (Helja) which was further purified by mannose-agarose affinity chromatography.  The aim of this work was to characterize the biological activity of Helja and to explore its potential applications. To assess agglutinantion properties, yeast (Saccharomyces cerevisiae) cells were incubated with growing concentrations of the purified protein. Helja clearly agglutinated these cells at a concentration of 120 ƒÊg/ml. Its carbohydrate-specificity was determined on the basis of the ability of different sugars to inhibit cell agglutination. Among the monosaccharides tested, D-mannose showed the greatest inhibitory effect, being 1.5 mM the minimal concentration required to avoid agglutination. These results confirm that Helja is a mannose specific lectin. The antifungal activity of this JRL was evaluated using human pathogenic fungi belonging to Candida sp. We show that 100 ƒÊg/ml of Helja partially inhibited the growth of Candida albicans and induced morphological changes on Candida tropicalis through pseudohyphae formation. On the other hand, the potential insecticidal effect of Helja against the bruchid Callosobruchus maculates was explored. To that aim Helja was coupled to fluorescein isothiocyanate (FITC) and its binding to larvae digestive tract was determined by fluorescent microscopy. The visualized Helja-FITC signals revealed the interaction of the jacalin with carbohydrate moieties on the tissue surface.  We concluded that Helja is a new member of the mannose-binding JRLs with cell agglutination capability, antifungal activity against human pathogenic fungi and potential insecticidal properties. Novel activities of Helja continue to be investigated. A novel sunflower lectin is described, whose biological properties may find practical applications to control of pathogens.