McCarthy J E, Schairer H U, Sebald W
EMBO J. 1985 Feb;4(2):519-26. doi: 10.1002/j.1460-2075.1985.tb03659.x.
The c, b and delta subunit genes of the Escherichia coli atp operon were cloned individually in an expression vector between the tac fusion promoter and the galK gene. The relative rates of subunit synthesis directed by the cloned genes were similar in vitro and in vivo and compared favourably with the subunit stoichiometry of the assembled proton-translocating ATP synthase of E. coli in vivo. The rate of synthesis of subunit c was at least six times that of subunit b and 18 times that of subunit delta. Progressive shortening of the long intercistronic sequence lying upstream of the subunit c gene showed that maximal expression of this gene is dependent upon the presence of a sequence stretching greater than 20 bp upstream of the Shine-Dalgarno site. This sequence thus acts to enhance the rate of translational initiation. The possibility that similar sequences might perform the same function in other operons of E. coli and bacteriophage lambda is also discussed. Translation of the subunit b cistron is partially coupled to translation of the preceding subunit c cistron. In conclusion, the expression of all the atp operon genes could be adjusted to accommodate the subunit requirements of ATP synthase assembly primarily by means of mechanisms which control the efficiency of translational initiation and re-initiation at the respective cistron start codons.
大肠杆菌atp操纵子的c、b和δ亚基基因分别克隆于一个表达载体中，位于tac融合启动子和galK基因之间。克隆基因所指导的亚基合成相对速率在体外和体内相似，并且与大肠杆菌体内组装的质子转运ATP合酶的亚基化学计量比相比具有优势。亚基c的合成速率至少是亚基b的6倍，是亚基δ的18倍。亚基c基因上游长间隔序列的逐步缩短表明，该基因的最大表达依赖于位于Shine-Dalgarno位点上游大于20 bp的一段序列的存在。因此，该序列起到增强翻译起始速率的作用。文中还讨论了类似序列在大肠杆菌和噬菌体λ的其他操纵子中可能发挥相同功能的可能性。亚基b顺反子的翻译部分与前面的亚基c顺反子的翻译偶联。总之，atp操纵子所有基因的表达可以主要通过控制各自顺反子起始密码子处翻译起始和重新起始效率的机制来进行调节，以适应ATP合酶组装的亚基需求。
