Functional characterization of Micropterus salmoides galectin-3 (MsGal-3B): a multifunctional immune effector with...

Galectins are evolutionarily conserved lectins that play pivotal roles in innate immunity. In this study, we functionally characterized a novel chimera-type galectin-3 homolog from largemouth bass (Micropterus salmoides), designated MsGal-3B. The open reading frame of MsGal-3B encodes a 258-amino acid protein containing a canonical carbohydrate recognition domain (CRD) and an N-terminal non-lectin region, typical of galectin-3 family members. Phylogenetic analysis revealed that MsGal-3B clusters with galectin-3 orthologs from Perciformes, suggesting functional conservation within this order. Recombinant MsGal-3B (rMsGal-3B) exhibited strong affinity for peptidoglycan (PGN) and β-glucan (GLU), and weak interaction with lipopolysaccharide (LPS). Microbial binding assays revealed broad recognition across Gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus), Gram-negative bacteria (Aeromonas veronii, Vibrio parahaemolyticus), and fungi (Saccharomyces cerevisiae, Pichia pastoris). Notably, rMsGal-3B selectively agglutinated Escherichia coli and M. luteus, but not A. veronii or S. cerevisiae, indicating ligand-dependent functional specificity. rMsGal-3B significantly suppressed the proliferation of E. coli, M. luteus, and S. cerevisiae, while showing no inhibitory effect on A. veronii, suggesting a narrow-spectrum antimicrobial profile. Additionally, rMsGal-3B exhibited hemagglutination activity, implying a potential role in host cell recognition or immune modulation. Collectively, these findings demonstrate that MsGal-3B functions as a multifunctional immune effector in M. salmoides, capable of selective microbial recognition, agglutination, and targeted antimicrobial activity. This study provides new insights into the role of teleost galectins in innate immunity and highlights their potential as molecular targets for disease control in aquaculture.