KNR50: a moonlighting bioactive peptide hidden in the C-terminus of bovine casein αS2 with powerful antimicrobial, antibiofilm, antiviral and immunomodulatory activities.

Milk is a primary nutrition source for newborns and adults and, in addition, is also a valuable reservoir of bioactive peptides. Many of these peptides are hidden as "cryptic" sequences in milk proteins and released in the bioactive form through protease digestions. Caseins, the most abundant proteins in bovine milk, host several cryptic bioactive peptides including those antimicrobials. In this study we report in-silico identification, production in recombinant form and extensive characterization of KNR50, a novel cationic antimicrobial peptide (CAMP) located at the C-terminus of bovine casein αS2. KNR50 shows antimicrobial activity against a large panel of bacteria and does not induce resistance development. In addition, KNR50 shows a remarkably wide spectrum of functional properties, as antibiofilm and antiviral activities, immunomodulatory and antioxidant properties as well as promising in-vivo anti-infective properties in a Caenorhabditis elegans model. These findings suggest that KNR50 could serve as a promising multifunctional agent with potential applications not only in combating infectious diseases and enhancing immune responses but also in non-clinical settings such as food preservation, where its antimicrobial properties could be exploited to extend shelf-life and improve food safety.