Purificação de uma lectina presente na esponja marinha Dysidea sp.

Abstract

Sponges are sessile animals belonging to the phylum Porifera, composed of a multicellular matrix that can be supported by calcium carbonate or silicon dioxide spicules, and can exhibit various shapes, colors, and sizes. In these organisms, lectins are found, which are proteins and glycoproteins present in living beings and viruses, that are not part of the immunoglobulin group and are characterized by having at least one carbohydrate recognition domain. The interaction between the protein and the carbohydrate does not imply cleavage or enzymatic alterations, thus not causing structural changes in the ligand. In poriferans, lectins can perform various functions such as cell interaction, spiculogenesis, and defense, in addition to having great biotechnological potential. The aim of this study was to purify and characterize a lectin present in the aqueous extract of the sponge Dysidea sp. The organisms were collected in the intertidal zone at Bitupitá beach, located in the municipality of Barroquinha, CE. The material was cut into small pieces and macerated against Tris buffer, pH 7.6, containing 150 mM NaCl and 5 mM cysteine (TBS/L-cys). Then, the crude extract was subjected to ammonium sulfate precipitation. An aliquot of the crude extract and the 0-70% fraction was used in hemagglutination and inhibition tests, and the rest of the fraction was applied to affinity chromatography on a lactose-agarose matrix. The retained proteins were eluted with TBS/L-cys buffer containing 0.3 M lactose and subsequently applied to molecular exclusion chromatography for obtaining the purified protein and to SDS-PAGE for assessing the degree of purity. The 0-70% fraction showed significant hemagglutinating activity against rabbit erythrocytes when a reducing agent was used and was inhibited by lactose and galactose, with MICs of 25 mM and 50 mM, respectively. The electrophoresis gel of the eluates from affinity chromatography showed 3 distinct bands of 45, 30, and 15 kDa, while molecular exclusion chromatography presented a single band of 30 kDa.