Primeiro relato de uma lectina relacionada ao fibrinogênio em esponjas marinhas: caracterização bioquímica, estrutural e avaliação do potencial antibiofilme da lectina de Aplysina cauliformis (Carter, 1822)

Abstract

Marine sponges are sessile invertebrates recognized for producing a vast chemical arsenal with biotechnological properties, with lectins standing out for their antimicrobial, anticancer, and immunomodulatory activities. Recently, studies with the lectin AcL (Aplysina cauliformis) revealed synergistic effects with antibiotics, highlighting the need for an in-depth biochemical and structural characterization, as well as an evaluation of its potential against bacterial biofilms. The present study aimed to isolate, purify, and biochemically and functionally characterize AcL, determining its primary and tertiary structures, as well as its interaction thermodynamic parameters and antibiofilm potential.The results revealed that AcL presents a molecular mass of approximately 35 kDa under reducing conditions and 66 kDa under nonreducing conditions, suggesting a dimeric organization stabilized by disulfide bonds. DLS analyses confirmed that the protein is predominantly in a stable dimeric state in solution, with a hydrodynamic diameter between 7 and 8 nm. Amino acid sequencing identified 13 peptides (40% coverage of the genomic sequence), revealing that AcL has 320 residues and is characterized as the first report of a marine sponge lectin containing a fibrinogen-related domain (FReD). Three-dimensional modeling demonstrated an unprecedented architecture for poriferans, composed of an N-terminal fibrillar domain (long alpha-helix) and a C-terminal beta-sandwich domain. In ITC assays, AcL demonstrated high affinity for the PSM glycoprotein (KD = 134 nM), with the interaction being driven mostly by entropic effects. Regarding antibiofilm activity, AcL strongly inhibited biomass formation in all tested strains, with reductions exceeding 80% for S. aureus at concentrations starting from 125 μg/mL, in addition to significant inhibition (over 50%) for S. epidermidis and a dose-dependent effect against E. coli. Although there was no drastic reduction in the count of viable cells at most concentrations, the effectiveness in destabilizing the biofilm biomass was compelling. It is concluded that AcL inaugurates a new class of lectins in the phylum Porifera, positioning itself as a promising molecule for the development of anti-virulence strategies and marine biotechnology.