螺旋链霉菌U-1941中PKSII型基因在淡青链霉菌tcmK变异株中的克隆(I)

利用螺旋霉素产生菌螺旋链霉菌(S trep tomy ces sp iramy ceticus U-1941)中发现的PK S II型基因,经测序和同源性比较证明在4174bp片段中含有PK S II型K S(K Sα)基因,该基因(pCG 4-K,aspA)由1229bp组成编码432个氨基酸,与产二素链霉菌A lpA和淡青链霉菌T cmK同源性分别为74.4%和69.7%。将含aspA基因的重组质粒pCG 4在四并菌素(tetracenom yc in C)产生菌(S.g laucescens GLA 4-26)tcmK基因缺陷型变异株中进行克隆,TLC分析表明转化子的发酵产物比对照株多一个明显的黄色斑点,该物质经分离、提纯后分析确定为一个含苯式结构的小分子化合物A S-5。

Cloning of type II polyketide synthase gene of Streptomyces spiramyceticus U-1941 in the S.glaucescens tcmK mutant

A gene sequence similar to type II polyketide synthase(PKS) gene was discovered from Streptomyces spiramyceticus U-1941.DNA sequence analysis of 4,174bp fragment showed an open reading frame,consisting of 1,229bp and encoding a protein AspA with 432 amino acids.Homology comparison(revealed) that the AspA protein was similar to ketoacyl synthase(KS) such as AlpA of S.ambofaciens and tcmK of S.glaucescens.The recombinant plasmid pCG4 containing aspA gene fragment was transformed into a tcmK mutant of S.glaucescens(GLA 4-26).By comparison of the TLC profile of the extraction product of transformant fermentation broth with the fermentation product of the host strain,a distinct yellow spot was observed.A benzoic compound with small molecular weight of AS-5 was identified after chemical isolation and purification from the fermentation broth of the transformant.