牛抗菌肽Bac7-Bac5融合基因在大肠杆菌中的过表达，纯化及抑菌活性

牛抗菌肽Bac7和Bac5是一种线性阳离子小分子多肽，在机体天然免疫和获得性免疫中都发挥着重要作用。本研究根据Gen bank中公布的牛抗菌肽bac7和bac5成熟肽基因序列，人工合成了融合基因Bac7-Bac5片段，克隆于原核表达载体pET32(a+)中构建了重组表达载体（pET-B7-B5），将其转化于E coli BL21(DE3) 中实现了重组蛋白B7-B5（rB7-B5）的过表达，表达的rB7-B5以包涵体形式存在，rB7-B5表达量约占细菌总蛋白的36.6％，分子量大小为33kD，与预测大小相符。以经Ni亲和层析柱纯化和多步透析法复性的rB7-B5，对猪胸膜肺炎放线杆菌和耐药性大肠杆菌具有很好的抑菌活性，本研究为新型抗菌制剂的研制和开发奠定了基础。

Overexpression of the fusion gene encoding bovine antimicrobial peptides Bac7-Bac5 in Escherichia coli, and purification and antimicrobial activity of the fusion protein

Bovine antimicrobial peptides Bac7 and Bac5 are linear cation micromolecular polypeptides, which play an important role in both innate and acquired immunity. Based on the gene sequences encoding mature bovine antimicrobial peptides bac7 and bac5 as registered in Genbank, the fragment of the fusion gene Bac7-Bac5 was synthesized and cloned into the prokaryotic expression vector pET32 (a ) to construct a recombinant expression vector, pET-B7-B5. The recombinant construct was then transformed into E.coli BL21 (DE3) to over-express the recombinant protein B7-B5 (rB7-B5). The expressed rB7-B5 was localized in inclusion bodies and accounted for 36.6% of total bacterial protein. The molecular weight of rB7-B5 was 33kDa, a figure consistent with the predicted value. Following purification by Ni affinity chromatography and stepwise renaturation by dialysis, rB7-B5 showed sound antimicrobial activity in porcine actinobacillus pleuropneumoniae and antibiotics-resistant E. coli. So a basis for the research and development of novel antibacterial preparations were provided.