Zebrafish CD59 has both bacterial-binding and inhibiting activities

• A mammalian cd59 homolog was identified and characterized in zebrafish.
• Zebrafish cd59 showed both stage- and tissue-specific expression.
• Recombinant CD59 was able to bind both Gram-negative and Gram-positive microbes.
• Recombinant CD59 was able to bind the microbial signature molecules LPS and LTA.
• Recombinant CD59 had some antimicrobial activity against E. coli and S. aureus.

CD59, known as protectin, usually plays roles as a regulatory inhibitor of complement, but it also exhibits activities independent of its function as a complement inhibitor. This study reported the identification and characterization of an ortholog of mammalian cd59 from zebrafish Danio rerio, which is similar to known cd59 in terms of both amino acid sequence and genomic structure as well as synteny conservation. We showed that zebrafish cd59 was maternally expressed in early embryos and expressed in a tissue-specific manner, with most abundant expression in the brain. We further showed that recombinant zebrafish CD59 was capable of binding to both the Gram-negative and Gram-positive bacteria as well as the microbial signature molecules LPS and LTA. In addition we demonstrated that recombinant zebrafish CD59 displayed slight antimicrobial activity capable of inhibiting the growth of E. coli and S. aureus. All these data indicate that zebrafish CD59 can not only binds to the bacteria and their signature molecules LPS and LTA but can also inhibit their growth, a novel role assigned to CD59.