红霉素抗性基因ermE在链霉菌中的表达及抗性测定

红霉素抗性基因ermE编码一种甲基化酶，可以对50S核糖体亚基上的23SrRNA进行甲基化修饰．甲基化作用可能引起核糖体构型变化，阻碍红霉素与50S核糖体亚基的结合，从而使宿主获得抗性．研究中将来自红色糖多孢菌（Saccharopolyspora erythraea）的ermE基因克隆到链霉菌高拷贝表达栽体pUWL201和plJ6021上组成型启动子ermEp＊和硫链丝菌素诱导型启动子PfipA的下游，构建出了链霉菌表达质粒pKIM4，pKIM7和pKIM8．将pKIM4，pKIM7和pKIM8分别转入S．lividans链霉菌中，每种转化子都能表现出明显的红霉素抗性，并且ermE基因在TK64／pKIM8转化子中还实现了高效表达．

The expression and resistance analysis of the erythromycin resistance gene ( erm E) in streptomyces lividans

The ermE gene of Saccharopolyspora erythraea,which coffers resistance to erythromycin,encodes a methylase that can modify 23S RNA to change the conformation of 50S ribosomal subunits.This change prevents erythromycin from combining to 50S ribosomal subunits.Consequently,the host can be resistant to erythromycin.In the study,the ermE gene was cloned from Saccharopolyspora erythraea into S.lividans on high-copy expression vector pUWL201 and pIJ6021.The ermE gene was insert- ed downstream of constitutive promoter ermEp and thiostrepton-induced promoter P_(?A) respectively to construct expression plas- mid pKIM4,pKIM7 and pKIM8.The ermE gene on the each expression plasmid made S.lividans remarkable resistance to eryth- romycin and the expression level of the ermE gene was enhanced highly on the expression plasmid pKIM8 in S.lividans 66 TK64.