Anti-lipopolysaccharide factors (ALFs), as main host-defense molecules of crustaceans, form a unique family of antimicrobial peptides (AMPs). MnALF4 is one isoform of ALFs isolated from the freshwater prawn Macrobrachium nipponense. In the present study, MnALF4 gene was successfully expressed in the yeast Pichia pastoris and the recombinant MnALF4 protein exhibited efficient and broad-spectrum antimicrobial activities against both Gram-positive bacteria and Gram-negative bacteria in vitro. When prawns were injected with rMnALF4 before bacterial challenge with E. coli, the recombinant protein effectively promote the elimination of bacteria by the host. It manifested that rMnALF4 could effectively kill the invading bacteria in vivo. Treatment with rMnALF4 led to remarkable changes in bacterial morphology, such as spheroidization, oversized bacteria, and cell lysis. In addition, rMnALF4 showed weak hemolysis activity to the rabbit red blood cells. Our work suggests that MnALF4 plays an important role in Macrobrachium immunity and is worthy of further investigation as a potential antibacterial agent with high efficacy against bacterial infection and low toxicity to host cells.

中文翻译：

---

东方河虾抗脂多糖因子基因在毕赤酵母中的重组表达及其特性分析

抗脂多糖因子（ALF）作为甲壳类动物的主要宿主防御分子，形成独特的抗菌肽（AMP）家族。MnALF4 是从淡水虾日本沼虾中分离出的 ALF 的一种亚型。本研究成功在毕赤酵母中表达MnALF4基因，重组MnALF4蛋白在体外对革兰氏阳性菌和革兰氏阴性菌均表现出高效、广谱的抗菌活性。当对虾在用大肠杆菌进行细菌攻击之前注射rMnALF4时，重组蛋白有效地促进宿主对细菌的消除。表明rMnALF4能有效杀灭体内入侵细菌。rMnALF4 处理导致细菌形态发生显着变化，例如球化、细菌过大和细胞裂解。此外，rMnALF4对兔红细胞表现出较弱的溶血活性。我们的工作表明，MnALF4 在沼虾免疫中发挥着重要作用，作为一种潜在的抗菌剂，具有高效对抗细菌感染和对宿主细胞低毒性的特点，值得进一步研究。