Acetylation inhibition of key lysine residue enhances antibacterial activity of rhamnose-binding lectin in pearl oyster, Pinctada fucata martensii

Pearl oyster, Pinctada fucata martensii (Pm) is a marine bivalve that plays a key role in pearl cultivation in the South China Sea. Rhamnose-binding lectin (RBL) is an essential component of its immune system. Recently, the regulatory role of acetylation in the innate immune response has gained significant attention. In this study, we investigated the impact of acetylation on PmRBL by constructing recombinant (r) PmRBL proteins with acetylation and deacetylation modifications at lysine residues K91 and K159 (rPmRBL: rPmRBL-K91R, rPmRBL-K91Q, rPmRBL-K159Q, and rPmRBL-K159R), and performing antibacterial and agglutination assays. The antibacterial assays showed that rPmRBL-K159R exhibited enhanced inhibition against specific bacteria. Additionally, the agglutination assays revealed that rPmRBL-K159R displayed stronger aggregation effects on Aeromonas hydrophila and Escherichia coli compared to rPmRBL-Wild. These findings suggest that acetylation at K91 and K159 influences the immune function of PmRBL, with decreased acetylation at K159 potentially enhancing its antibacterial activity and altering its bacterial targets, making K159 a key regulatory site. This study provides new insights into the immune function of PmRBL from the perspective of acetylation modification, offering a deeper understanding of the regulatory mechanisms involving K91 and K159, and presenting new directions for exploring the immune regulation of P. f. martensii . • rPmRBL-K159R enhanced inhibition against bacteria. • The acetylation levels at K91 and K159 affect the immune function of PmRBL. • K159 related to the recognition functions of PmRBL with specific polysaccharides.