A C‐type lectin with antibacterial activity in weather loach, <i>Misgurnus anguillicaudatus</i>

TLDR

C‑type lectins are carbohydrate‑binding proteins that act as pattern recognition receptors and play key roles in immunity. The study aimed to isolate a novel nattectin‑like C‑type lectin, MaCTL, from the weather loach *Misgurnus anguillicaudatus*. MaCTL is a 165‑residue peptide with a signal peptide and a single C‑type lectin domain containing a galactose‑specific QPD motif and a conserved Ca²⁺‑binding site. MaCTL expression was up‑regulated after immune challenge, and recombinant protein exhibited Ca²⁺‑dependent hemagglutination, bacterial agglutination, binding to diverse bacteria and polysaccharides (LPS, PGN), and antimicrobial activity, indicating its role in the loach’s antibacterial defense.

Abstract

Abstract C‐type lectins are carbohydrate‐binding proteins that play important roles in immunity by serving as pattern recognition receptors. In the present study, a novel nattectin‐like C‐type lectin was obtained from the weather loach, Misgurnus anguillicaudatus , designated as MaCTL. MaCTL encodes a peptide with 165 amino acids, with a signal peptide and a single C‐type lectin domain (CTLD), containing a galactose‐specific QPD motif and a conserved Ca 2+ ‐binding site. Transcripts of MaCTL were significantly upregulated after immune challenge with its pathogen A. hydrophila . In vitro assays with recombinant MaCTL protein revealed that it exhibited hemagglutinating and bacterial agglutinating activities, in a Ca 2+ ‐dependent manner. MaCTL was found to bind to a wide range of bacteria, as well as bind to bacterial polysaccharides LPS and PGN. Moreover, MaCTL displayed antimicrobial activity by inhibiting the growth of bacteria. These results collectively suggest that MaCTL is involved in the antibacterial defence of weather loach.