Caracterização, estudos estruturais e potencial antibacteriano de lectinas isoladas das esponjas marinhas Haliclona (Reniera) implexiformis e Aplysina fistularis

Abstract

Sponges are the most primitive aquatic animals on the planet and in recent decades they have stood out in the biotechnological area for producing a variety of molecules with unique structural characteristics and presenting the potential to provide future medicines against human diseases, among the molecules produced are lectins, which are proteins or glycoproteins of non-immune origin capable of reversibly binding carbohydrates without altering their structure. The objective of this work was to purify, biochemically and structurally characterize lectins present in two sponges found in the coast of Ceará, Haliclona (Reniera) implexiformis and Aplysina fistularis, and from the isolation evaluate their antibacterial potential against pathogenic strains. Both lectins were purified on a Sepharose™ matrix and named HiL (Haliclona implexiformis lectin) and AfiL (Aplysina fistulares lectin). HiL showed hemagglutinating activity and was inhibited mainly by galactosides and PSM (porcine stomach mucin), being more active at alkaline pH with resistance at acidic pH and did not undergo total denaturation at temperatures up to 60°C. The results predict that the lectin is a disulfide-linked dimer with an average molecular mass of 35,876 ± 2Da and with a predominance of β conformation. The primary structure of HiL was partially determined and showed no similarity to any protein. HiL showed a significant reduction in the number of viable Staphylococcus biofilm cells and was able to cause S. aureus agglutination. In relation to AfiL, there was inhibition of the hemagglutinating activity by galactose derivatives with Galβ1→4 and PSM binding. The lectin was active at alkaline pH, resistant to temperatures up to 80°C, estimated mass of 224 kDa in the native conformation, and presented a predominant secondary structure of β conformation and disordered structures. The primary structure of AfiL was partially determined, it showed no similarity with any member of the animal lectin families, however, it showed 33.33% identity and 69.26% similarity with a putative protein encoded in the genome of the marine sponge Amphimedon queenslandica. AfiL inhibited the biofilm formation of strains of gram-negative and gram-positive bacteria, and also caused a bacteriostatic effect on methicillin- and tetracycline-resistant S. aureus strains. Thus, two new lectins from marine sponges were discovered, characterized and verified their antibacterial potential, making it important for the biotechnological advance of marine natural resources with biomedical potential.