Breeding of efficient strains of saccharomyces cerevisiae to produce heterologous gene product.

对生产外源基因产品的高效菌株的选育进行了研究。以酿酒酵母（s . cerevisiae）的聚半乳糖醛酸酶（PG）基因编码为标记，分离出了一种导致异源基因产物生产过剩表型的突变体。结果如下：(1)获得了一个导致PG过量分泌的突变体。突变体（SSM5-2）的PG产量是亲本的10 ~ 30倍。(2)突变体细胞膜脂质含量与亲本不同，制备感态细胞的条件也与亲本不同。建立了一种简单有效的质粒转化方法。(3) SSM5-2为温度敏感致死突变体，其生长因PG的产生而受阻，并被证实为G2阻滞。发现G2捕集被Ca^<2+>回收。(4)在马氏K. marxianus PG基因上游区域发现了一个促进PG生成的基因（PGPPF）。确定了PGPPF的碱基序列。

The research on breeding of efficient strains to produce heterologous gene product have been done. A mutant responsible for an overproduction phenotype on heterologous gene product in S. cerevisiae has been isolated, using the gene coding for polygalacturonase (PG) from KZLwvem"s marxianus as a marker.The results obtained are as follows :(1) A mutant responsible for an oversecretion of PG was obtained. The mutant (SSM5-2) produced PG by 10- to 30-fold in parent strain.(2) Contents of lipids in the cell membrane of the mutant was different from those of parent strain, and the conditions for preparing competent cell were also different from parent strain. A simple and efficient method for transformation with plasmids was established.(3) SSM5-2 was temperature-sensitive lethal mutant and it growth was arrested with the production of PG, and it was confirmed to be G2 arrest. The G2 arrest was found to be recovered by Ca^<2+>.(4) A gene which promote the PG production (PGPPF) was found on upstream region of PG gene of K. marxianus. The base sequence of PGPPF was determined.