重组猪乳铁蛋白N端的高效表达及抑菌活性检测

High-level expression and antimicrobial activity of recombinant N-terminal porcine lactoferrin

为获得表达猪乳铁蛋白基因的重组菌株,并检测其表达的重组猪乳铁蛋白抑菌活性,应用RT-PCR方法从泌乳3d后母猪乳腺组织中扩增了猪乳铁蛋白N端1077bp的PLF-N基因片段,与GenBank上发表的4株猪乳铁蛋白基因序列相比,核苷酸同源性均达到99%以上。为了得到高表达量的PLF-N基因,以扩增的PLF-N片段为参考模板,经过密码子优化,全基因合成了编码猪乳铁蛋白N端的基因PLF-NS。将其定向插入到原核表达载体pET-30b中,转化大肠杆菌BL21,获得了表达PLF-NS的重组菌pET-PLF-NS/BL21;经IPTG诱导,并对表达条件进行优化,以及通过SDS-PAGE和Western blotting分析均表明猪乳铁蛋白得到了正确表达,其产物分子量约为42kDa,最优表达条件下蛋白表达量占菌体总蛋白的32%,表达产物以包涵体形式存在。包涵体经裂解、纯化、复性处理后纯度达到98%。用琼脂孔穴扩散抑菌法检测表明重组猪乳铁蛋白具有明显的抑菌作用。表明通过基因优化对表达量低的基因进行改造使之高效表达,是一种提高表达效率的有效手段。

Lactoferrin in milk is a multifunctional protein. In addition, lactoferrin has antiviral, antifungal and antiparasitic activity. In this study, the N-terminus from porcine lactoferrin （PLF-N） was designed to express the antimicrobial action of recombinant porcine lactoferrin. We cloned a 1077 bp fragment of the PLF gene from mammary gland tissue of the lactating sow at the third day. Comparing nucleotide sequence with four strains of PLF gene published on GenBank, the homology was more than 99%. With the reference template of the cloned fragment of PLF-N and optimizing codon bias, we synthesized the gene of N-terminus encoding porcine lactoferrin （PLF-NS）. The high expression gene of PLF-NS was cloned into the fusion expressionvector pET30b and expressed in E. coli BL21 （DE3）. After induced with Isopropyl β-D-1-Thiogalactopyranoside （IPTG）, the target fusion protein was successfully expressed and identified in inclusion bodies by SDS-PAGE and Western blotting. The protein had a molecular weight of 42 kDa and accounted for 32% of the total cellular protein. After purification and renaturation, the purity of the expressed protein was 98%. The expressed PLF-NS protein showed obviously antibacterial activity. This method provides an excellent way for high expression of antimicrobial proteins when optimizing codon bias.