纯化标签的不同位置对Δ6脂肪酸脱饱和酶异源表达的影响

Effects of purification tag positions on the heterologous expression of Δ6 fatty acid desaturase

摘要:

[背景] 目前利用酵母表达系统已鉴定了多种物种中的Δ6脂肪酸脱饱和酶（FADS6）。由于FADS6是一种具有多个跨膜螺旋的膜蛋白，使得其大量表达和纯化具有挑战性。[目的] 探索FADS6的高效表达策略，研究纯化标签添加的位置对高山被孢霉FADS6I （MaFADS6I）重组表达效率的影响。[方法] 在毕赤酵母表达载体中插入串联亲和标签HRV 3C-Protein A-His，利用改造后的载体构建带有N端或C端标签的MaFADS6I表达载体；通过电转化获得毕赤酵母重组表达菌株；利用斑点印迹杂交（Dot blot）、聚丙烯酰胺凝胶电泳（SDS-Polyacrylamide Gel Electrophoresis，SDS-PAGE）和免疫印迹（Western blot）分析重组蛋白的表达水平，并利用气相色谱-质谱（Gas Chromatography-Mass Spectrometry，GC-MS）分析检测MaFADS6I催化生成的脂肪酸。[结果] 通过大量的毕赤酵母转化子筛选，最终获得高效表达MaFADS6I的毕赤酵母重组菌，证实各转化子的表达具有差异性，MaFADS6I的C端带有纯化标签较N端更有利于表达。[结论] 在MaFADS6I的C端添加纯化标签比在N端添加更有利于该蛋白在酵母系统中的表达以及底物的转化，为进一步探究FADS6高效表达和结构功能奠定了基础。

Abstract:

[Background] At present, the characteristics of Δ6 fatty acid desaturase (FADS6) from various species have been identified through the yeast expression system. Since FADS6 is a multiple transmembrane protein, it is challenging to achieve large-scale expression and purification. [Objective] To construct a high-efficiency expression strategy of FADS6, the present study will analyze the influence of the location of the purification tag on heterologous expression of Mortierella alpina FADS6I (MaFADS6I). [Methods] Tandem affinity tag HRV 3C-Protein A-His was added into the Pichia pastoris vector, followed by the insertion of MaFADS6I sequence to construct recombinant vectors with the N-terminal or C-terminal tag, respectively. Recombinants were obtained through electro-transformation. The protein expression level of MaFADS6I in recombinant strains was analyzed by dot blot hybridization (dot blot), polyacrylamide gel electrophoresis (SDS-PAGE) and western blot, and the fatty acids catalyzed by MaFADS6I was detected by gas chromatography-mass spectrometry (GC-MS). [Results] Transformants with different MaFADS6I expression levels and catalytic activities were obtained. compared with the N-terminal tag, the C-terminal tag was more conducive for the expression and catalytic activity of MaFADS6I. [Conclusion] MaFADS6I with C-terminal purification tag is more conducive to the expression of the protein in the yeast system and the conversion of substrates than with N-terminal tag, providing a foundation for the high-efficiency expression and structural and functional studies of FADS6.