Caracterização estrutural e avaliação do potencial antibacteriano em combinação com antibióticos de uma lectina da esponja marinha aplysina lactuca

Abstract

Sponges are animals belonging to the phylum Porifera, one of the oldest and with the simplest cellular organization among the metazoans. The genus Aplysina was inserted into the Order Verongideae due to the presence of brominated compounds with high biological effects arising from their metabolism. In addition to these compounds, lectins, proteins capable of binding to carbohydrates without altering their structure, have already been identified in this genus. Lectins have the ability to interact with target glycans and trigger varied responses, including inhibiting the development of various pathogens. Determining the amino acid sequence of these proteins is essential to better understand their functions, but in these organisms few primary lectin structures have been completely determined. Among the lectins purified from marine sponges, only one has its three-dimensional structure determined. Thus, the objective of this work was to structurally characterize and evaluate the antibacterial potential, in association with different antibiotics, and the antibiofilm effect of the lectin from the marine sponge Aplysina lactuta (ALL). ALL is a 15 kDa protein that oligomerizes to form a 60 kDa tetramer. The lectin showed affinity for the glycoproteins fetuin, asialo fetuin, mucin type III and bovine submaxillary mucin type I. The sequences of two isoforms of ALL, named ALL-a and ALL-b, were completely determined by mass spectrometry in association with degradation of Edman. ALL-a and ALL-b have 144 amino acids with molecular masses of 15,736 Da and 15,985 Da, respectively. Both have amino acid sequences containing conserved residues typical of the galectin family. The predicted three-dimensional structures of ALL-a and ALL-b revealed a β sandwich architecture with two antiparallel β sheets. The binding site prediction shows interactions involving saccharides as in galectins. ALL is a protein with antibacterial potential, when in association with ampicillin the lectin potentiated its antibiotic effect, in addition to having an antibiofilm effect. Thus, ALL shows to be a lectin with high potential for the development of new antibacterial drugs.