Characterization of the active fragments of Spodoptera litura Lebocin‐1
2020
Yang, Li‐Ling | Zhan, Ming‐Yue | Zhuo, Yu‐Li | Dang, Xiang‐Li | Li, Mao‐Ye | Xu, Yang | Zhou, Xiu‐Hong | Yu, Xiao‐Qiang | Rao, Xiang‐Jun
Insects can produce various antimicrobial peptides (AMPs) upon immune stimulation. One class of AMPs are characterized by their high proline content in certain fragments. They are generally called proline‐rich antimicrobial peptides (PrAMPs). We previously reported the characterization of Spodoptera litura lebocin‐1 (SlLeb‐1), a PrAMP proprotein. Preliminary studies with synthetic polypeptides showed that among the four deductive active fragments, the C‐terminal fragment SlLeb‐1 (124‐158) showed strong antibacterial activities. Here, we further characterized the antibacterial and antifungal activities of 124‐158 and its four subfragments: 124‐155, 124‐149, 127‐158, and 135‐158. Only 124‐158 and 127‐158 could agglutinate bacteria, while 124‐158 and four subfragments all could agglutinate Beauveria bassiana spores. Confocal microscopy showed that fluorescent peptides were located on the microbial surface. Fragment 135‐158 lost activity completely against Escherichia coli and Staphylococcus aureus, and partially against Bacillus subtilis. Only 124‐149 showed low activity against Serratia marcescens. Negative staining, transmission, and scanning electron microscopy of 124‐158 treated bacteria showed different morphologies. Flow cytometry analysis of S. aureus showed that 124‐158 and four subfragments changed bacterial subpopulations and caused an increase of DNA content. These results indicate that active fragments of SlLeb‐1 may have diverse antimicrobial effects against different microbes. This study may provide an insight into the development of novel antimicrobial agents.
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