重组毕赤酵母甲醇利用表型与基因拷贝数对外源基因表达的影响

毕赤酵母是目前最优秀的外源蛋白表达系统之一。本文着重对重组毕赤酵母甲醇利用表型（Mut+型、MutS型和Mut-型）、基因剂量对外源蛋白高效表达的影响机理进行综述。MutS型的比生长速率和蛋白产率比Mut+型低、发酵周期长、副产物（如乙醇、乙酸等）形成速率不同。外源基因拷贝数对外源蛋白的影响主要有三种情况：（1）高基因拷贝数对外源蛋白表达水平有明显的正效应作用；（2）基因拷贝数增加反而降低了表达水平，即负效应作用；（3）重组蛋白表达与基因剂正相关，之后则表现负相关关系，这可能与外源蛋白翻译后加工有关（如二硫键形成、折叠等）,而与分子伴侣共表达可促进外源蛋白的高表达。

Influences of methanol utilization phenotype and gene dosage on heterologous protein expression in recombinant Pichia pastoris

The methylotrophic yeast,Pichia pastoris, has been one of most widely used expression system for heterologous proteins production in the past decades.The influences of methanol utilization phenotypes (i.e Mut , Muts and Mut-) and gene dosage on recombinant protein expression in genetically engineered Pichia pastoris woere reviewed. Strains with different phenotype not only exhibit different methanol utilization rate and growth rate, but also differ in terms of foreign protein production and byproducts production. Gene dosage has a complex impact on heterologous protein expression. Foreign gene copy number could positively correlate to protein production, whereas the negative correlation often occurs especially when gene dosage goes high. The latter might be related with post-translational processing of target protein like disulfide bond formation, folding, etc and some studies show that protein production yield can be enhanced by co-expression of proteins with chaperon activity, like PDI(protein disulfide isomerise). Physiologic profiles of strains with different gene dosage were also compared.