Structural Determinants of Species-Specific Mannose-Binding Lectin Recognition of Brucella melitensis M-Antigen: A Comparative Genomics and Molecular Dynamics Study

Mannose-binding lectin (MBL) is a pivotal innate immune protein that recognizes pathogen surface glycans, including Brucella melitensis ’s immunosuppressive M-antigen. This study deciphers how interspecies MBL variation influences M-antigen binding and informs model selection for anti-brucellosis strategies. Using comparative genomics, phylogenetics, and computational biophysics, we analyzed MBL from eight species (human, cattle, sheep, goat, horse, camel, rat, chicken). Phylogenetic reconstruction (UPGMA/JTT + G) revealed evolutionary clustering of cattle-sheep (98% support) and human-horse (75% support), with chicken as an outgroup. MBL gene length (4,223–27,399 nucleotides) and GC content (38.19–46.74%) varied significantly, though CRD domains were universally conserved (E-values ≤ 5.6×10⁻²³). Homology models validated by Ramachandran plots (> 88% residues favored) facilitated molecular docking, identifying cattle MBL with the strongest M-antigen affinity (− 9.2 kcal/mol), followed by human (− 9.1 kcal/mol) and horse (− 9.0 kcal/mol). Interaction profiling highlighted cattle’s stable hydrogen-bond network (9 bonds; e.g., ASN215: 2.04 Å) and hydrophobic packing (PHE196/PRO214), while horse relied on more bonds (12) but with greater instability. Molecular dynamics (150 ns simulations) confirmed cattle MBL’s superior complex stability: lower RMSD (≤ 2.5 nm vs. horse: 5.8 nm), consistent radius of gyration, and sustained hydrogen bonds (2–6 bonds vs. horse: 2–12 fluctuating bonds). These results demonstrate cattle MBL’s structural and functional synergy with the M-antigen, mirroring human MBL’s binding efficacy. We propose cattle as an optimal model for translational brucellosis research and highlight its potential in breeding-resistant livestock via MBL-targeted genetic strategies.