狐狸生长激素基因的克隆及其在毕赤酵母中的表达

为制备重组狐狸生长激素(fGH),采用RT-PCR方法,从银狐垂体中扩增fGHcDNA基因,利用SnaBI和NotI位点将fGH基因插入到酵母分泌型表达载体pPIC9K中α-因子信号肽的下游,构建成fGH基因的酵母分泌型表达载体pPIC9K/fGH,载体经SalI酶切线性化后,通过电转移将线性化的pPIC9K/fGH转化到组氨酸缺陷型酵母宿主菌GS115中。然后利用不含氨基酸的以葡萄糖为碳源的培养基(MD)和以甲醇为碳源的培养基(MM)筛选出组氨酸His+型和甲醇利用正型(Mut+)酵母重组体,再经G418加压筛选出高拷贝fGH基因的重组酵母,经摇瓶发酵培养和甲醇诱导使fGH进行分泌表达。结果表明本实验扩增的fGH基因序列与GenBank发表的序列基本一致,发酵液经SDS-PAGE和Western blotting检测证明构建的重组酵母能够分泌表达fGH,表达的fGH占发酵液总蛋白的34%,表达量达119mg/L发酵液。

Cloning and expression of fox growth hormone gene in Pichia pastoris

To prepare recombinant fox growth hormone (fGH), we amplified its cDNA from silver fox pituitary tissue by RT-PCR and cloned into yeast shuttle vector pPIC9K down stream of α-factor signal peptide sequence by SnaB I and Not I restriction sites. The recombinant secretion vector pPIC9K/fGH, linearized by Sal I, was transformed into histidine-deficient Pichia pastoris strain GS115 by electroporation. We selected His~+-transformed methylotropic (His~+, Mut~+) yeast using histidine-absent medium containing dextrose (MD) or methanol (MM) as the only carbon source, and then screened the recombinant GS115 with multi-copy fGH genes by G418. The secretive expression of fGH was performed under the induction of methanol in shaking flask culture. The results showed that the fGH cDNA sequence amplified in this paper was basically in consistence with the published in GenBank. We achieved the secretive expression of recombinant fGH identified by SDS-PAGE and Western blotting. The fGH expression level was 119 mg/L, accounted for 34% of total proteins in fermentation medium.