Cleary P P, Campbell A, Chang R
Proc Natl Acad Sci U S A. 1972 Aug;69(8):2219-23. doi: 10.1073/pnas.69.8.2219.
Biotin independence in E. coli requires five closely linked genes, bioA, bioB, bioF, bioC, and bioD. The residual gene activity of deletion mutants has been studied by complementation and enzyme assays. Deletion of the left end of the bioA gene does not impair expression of the remaining genes, but deletions from the left extending into bioB abolish all gene expression. Nonsense mutations in bioB reduce expression of bioC, bioF, and bioD. Therefore, the four genes, bioB, bioF, bioC, and bioD, are transcribed as a unit from left to right, from a promotor located between bioA and bioB. Expression of the bio genes is repressible by added biotin. Deletions removing the left end of bioA do not affect repressibility of bioD. Therefore the operator, as well as the promoter, lie to the right of bioA. One deletion that removes bioA, bioB, and bioF renders the bioD gene constitutive, presumably by fusion to an unknown operon. Therefore, the operator lies to the left of bioC.
大肠杆菌中生物素自主性需要五个紧密连锁的基因，即bioA、bioB、bioF、bioC和bioD。已通过互补和酶分析研究了缺失突变体的残余基因活性。bioA基因左端的缺失不会损害其余基因的表达，但从左端延伸至bioB的缺失会消除所有基因的表达。bioB中的无义突变会降低bioC、bioF和bioD的表达。因此，bioB、bioF、bioC和bioD这四个基因从位于bioA和bioB之间的启动子开始，作为一个单元从左向右转录。生物素基因的表达可被添加的生物素抑制。去除bioA左端的缺失不会影响bioD的可抑制性。因此，操纵基因以及启动子位于bioA的右侧。一个去除bioA、bioB和bioF的缺失使bioD基因组成型表达，推测是通过与一个未知操纵子融合。因此，操纵基因位于bioC的左侧。
