Honeybee (Apis cerana) major royal jelly protein 4 exhibits antimicrobial activity

Major royal jelly proteins (MRJPs) are important protein components of bee royal jelly (RJ) and exhibit various biological and pharmacological activities. The antimicrobial activities of the royalisin and the jelleines contained within MRJP 1 and MRJP 2 in RJ have been elucidated. However, the antimicrobial effects of other MRJPs remain largely unknown. In this study, we demonstrated the antimicrobial activity of the Asiatic honeybee (Apis cerana) MRJP 4 (AcMRJP4). Recombinant AcMRJP4 was expressed as a 63-kDa protein in baculovirus-infected insect cells. We examined the antimicrobial activity of recombinant AcMRJP4 against bacteria, fungi, and yeast. The mechanisms underlying the antimicrobial activity of AcMRJP4 were assessed using western blot analysis, immunofluorescence staining, and scanning electron microscopy. Recombinant AcMRJP4 bound to the cell walls of bacteria, fungi, and yeast and induced structural damage in the microbial cell walls. AcMRJP4 has an antimicrobial role and exhibits a broad spectrum of antimicrobial activities against bacteria, fungi, and yeast. We demonstrated that AcMRJP4 functions as an antimicrobial agent with activity against bacteria, fungi, and yeast. Together, our data identified a novel function of MRJP 4 as an antimicrobial agent.