利用双启动子表达载体pDH2-YggG-Ptac-Era研究E. coli Era和YggG 蛋白间的相互关系

yggG是从大肠杆菌全基因组文库中钓取并克隆的Era结合蛋白基因，研究表明该基因表达的YggG294(amino acids 1-294)蛋白对宿主菌的生长具有强烈的抑制作用。为了阐明YggG与Era间的相互关系，构建可同时可控性表达Era和YggG294蛋白的双启动子表达载体。利用所构建的双启动子表达载体在同一细胞中同时可控性地表达YggG294与Era蛋白。结果显示，在不表达和少量表达YggG294的细菌细胞内，Era 的表达量与总蛋白量的比值随着诱导时间增加而增高，而YggG294大量表达的细菌内Era 的表达量与总蛋白量的比值基本保持不变；Era 蛋白的预表达对YggG294表达所引起的细菌生长率下降无影响。由此可以推论，YggG294的过表达引起宿主菌生长抑制进而影响了Era蛋白的进一步表达，而YggG294的过表达引起宿主菌生长抑制与YggG和Era蛋白间的相互作用无关

Analysis of the relationship between Era and YggG in E. coli by double-promoter expression vector pDH2-YggG-Ptac-Era

yggG, a Era-binding protein gene, was isolated and cloned from the E.coli genomic DNA library. Previous studies indicated that the product of yggG gene, YggG294(amino acids 1-294), strongly inhibited the growth of host bacteria and caused the death of bacteria cells. To elucidate whether Era is related to the death of bacterial cells expressed YggG294,A double promoter expression vector that can express YggG294 and Era proteins controllably in cells was constructed. Using this vector to express YggG294 and Era protein in the same E.coli cells, then analyzed the relation between YggG294 and Era. The results showed that the ratio of Era proteins to total proteins increased with the increase of induction time in E.coli cells without YggG294 expression and with little YggG294 expression;the ratio of Era proteins to total proteins seemed to be a constant level in E.coli cells overexpressing YggG294;but we could not detect any Era hydrolyzate in E.coli cells overexpressed YggG294 could not be detected. The results also showed that pre-expression of Era protein did not produce any effect on the growth inhibition of E.coli cells caused by YggG294. These results indicate that YggG294 can not hydrolyze Era protein in E.coli cells, and that YggG-Era interaction is not associated with the death of bacteria expressed YggG294. It is thus reasonable to draw a conclusion that Era is not associated with the growth inhibition of E.coli cells caused by YggG294. YggG294 inhibits the growth of bacteria by other way.