• Journal of Microbiology and Biotechnology
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• 제22권4호
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• pp.479-483
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• 2012

The secretory efficiency of recombinant xylanase xynB from yeast Pichia pastoris between the ${\alpha}$-factor preprosequence and a classical mammalian signal peptide derived from bovine ${\beta}$-casein was compared. The results showed that although the bovine ${\beta}$-casein signal peptide could direct high-level secretion of recombinant xylanase, it was relatively less efficient than the ${\alpha}$-factor preprosequence. In contrast, the bovine ${\beta}$-casein signal peptide caused remarkably more recombinant xylanase trapped intracellularly. Real-time RT-PCR analysis indicated that the difference in the secretory level between the two signal sequences was not due to the difference in the transcriptional efficiency.

• 미생물학회지
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• 제36권3호
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• pp.236-241
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• 2000

효모 Saccharomyces cerevisiae를 숙주 세포로 이용하여 활성형의 항균펩티드를 생산하기 위한 model system으로서 쉬파리 유래 defensin의 합성 유전자를 GAP promoter, mating factor $\alpha$1 (MF$\alpha$1)의 preprosequence 및 GAL7 transcription terminator의 조절하에 있는 재조합 plasmid pGMD18을 제작한 후 Saccharomyces cerevisiae에 형질전환하여 growth inhibtion zone assay를 통해 항균활성을 보유한 재조합 효모를 선별하였다. 재조합 효모의 성장 속도와 defensin의 분비능을 증가시키기 위하여 최적의 배지 조성과 배양조건을 결정하였다. 재조합 효모의 defensin 생산을 위한 최적 배양조건을 조사한 결과 0.4% yeast extract, 유기질소원 2% corn steep liquor, 탄소원 2.5% glucose, 0.05% $C_2CO_3$를 포함한 배지에서 초기 pH3 그리고 배양온도 $28^{\circ}C$의 경우가 세포성장과 defensin 의 항균활성이 가장 우수하였다. 이 조건으로 배양을 수행한 결과 YPD 배지에서 배양한 조건보다 약 2배의 세포 성장과 약 4배의 defenzin 생산을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제24권2호
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• pp.144-151
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• 2014

Increasing the gene copy number has been commonly used to enhance the protein expression level in the yeast Pichia pastoris. However, this method has been shown to be effective up to a certain gene copy number, and a further increase of gene dosage can result in a decrease of expression level. Evidences indicate the gene dosage effect is product-dependent, which needs to be determined when expressing a new protein. Here, we describe a direct detection of the gene dosage effect on protein secretion through expressing the enhanced green fluorescent protein (EGFP) gene under the direction of the ${\alpha}$-factor preprosequence in a panel of yeast clones carrying increasing copies of the EGFP gene (from one to six copies). Directly examined under fluorescence microscopy, we found relatively lower levels of EGFP were secreted into the culture medium at one copy and two copies, substantial improvement of secretion appeared at three copies, plateau happened at four and five copies, and an apparent decrease of secretion happened at six copies. The secretion of EGFP being limiting at four and five copies was due to abundant intracellular accumulation of proteins, observed from the fluorescence image of yeast and confirmed by western blotting, which significantly activated the unfolded protein response indicated by the up-regulation of the BiP (the KAR2 gene product) and the protein disulfide isomerase. This study implies that tagging a reporter like GFP to a specific protein would facilitate a direct and rapid determination of the optimal gene copy number for high-yield expression.