Purificação, caracterização e avaliação de toxicidade de uma nova lectina das sementes de Bauhinia rufa (Bong.) Steud

Abstract

The interaction of cell-surface glycans with proteins has an important role in numerous vital functions to biological systems and lectins present themselves as an excellent tool for establishing studies of protein-carbohydrate interaction and specificity. Plant lectins stand out as one of the largest fields of study, given a special focus for the Leguminosae (Fabaceae) family, which presents several proteins already purified and characterized. This family also comprises the Cercidoideae subfamily, which presents the genus Bauhinia, also known as “cow's foot” or “cow's claw”. Regarding the Bauhinia lectins numerous biological activities have been reported such as inhibition of cancer cell growth, antinociceptive, anti and pro-inflammatory, insecticide, and antifungal activity. In this study, a new lactose-binding lectin, named BRL, has been purified from seeds of Bauhinia rufa (Bong.) Steud by affinity chromatography using an agarose-lactose column. BRL hemagglutinated rabbit erythrocytes (native and treated with proteolytic enzymes) and was strongly inhibited by α-lactose, followed by GalNAc, D-galactose, melibiose and rhamnose. By SDS-PAGE analysis, BRL profile is presented as a single band with an apparent molecular mass of 35 kDa (in the presence and absence of βmercaptoethanol). BRL was shown to be a stable glycoprotein (9.34% carbohydrate content) maintaining its activity after exposure at 60ºC for one hour and optimum activity in pH between 5.0 and 6.0. The lectin also presents a metal dependence (Ca 2+and Mg 2+) and showed no toxicity against Artemia nauplii. The present work aimed to purified, study the specificity and physicochemical properties of a new lectin from Bauhinia rufa, as well as evaluate its toxicity effect against Artemia sp. nauplii.