Abstract
Gloverin is one of the glycine-rich antimicrobial peptide exclusively found in Lepidoptera insects. It is generally activated through the innate immune system in insects. In this study, recombinant Gloverin2 from Bombyx mori (BmGlv2) was synthesized using a prokaryotic expression system. Circular dichroism spectroscopy showed that the recombinant BmGlv2 has random coil structure, which is relatively stable at the temperatures ranging from 15 to 82.5 °C. Antimicrobial activity analysis revealed that BmGlv2 significantly inhibited the growth of gram-negative bacteria, Escherichia coli JM109 and Pseudomonas putida, by disrupting cell integrity. Western blotting and immunofluorescence analyses suggested that BmGlv2 absorbed on the cell surface after incubation, which might be the first step in the antibacterial process. Our results also proved that the cell wall component lipopolysaccharides (LPS) induce a conformational change in BmGlv2 from a random coil to α-helix. Subsequently, α-helical BmGlv2 would recruit more BmGlv2 and form higher aggregation state. Collectively, these findings expand our understanding of antibacterial mechanism of BmGlv2.
Highlights
Silkworm (Bombyx mori) is an important economic insect and a classic model for studying Lepidoptera insects as well
Glv was first identified in Hyposphora cecropia (HcGlv) [9] and inhibits the growth of gram-negative bacteria E. coli D21f2
The BmGlv2 cDNA encodes a 173 amino acid protein with a signal peptide composed of 18 amino acid residues, indicating that BmGlv2 might be secreted into the extracellular milieu
Summary
Silkworm (Bombyx mori) is an important economic insect and a classic model for studying Lepidoptera insects as well. Glv was first identified in Hyposphora cecropia (HcGlv) [9] and inhibits the growth of gram-negative bacteria E. coli D21f2. Previous studies have shown that Glv mainly exerts antibacterial effects on gram-negative bacteria, fungi and viruses [11,12,13]. Structural and biochemical analyses suggested that BmGlv interacts with cell wall component LPS and accumulates on the surface of the bacterial cell through a conformational change. These findings led us to propose a putative model of BmGlvs against E. coli and provide clues for better understanding of the mechanism of action of Glvs
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