Duckworth D H, Pinkerton T C
Department of Immunology and Medical Microbiology, University of Florida College of Medicine, Gainesville 32610.
Plasmid. 1988 Nov;20(3):182-93. doi: 10.1016/0147-619x(88)90025-x.
The colicin Ib (ColIb) plasmid genes that inhibit the replication of the T5-like and T7 bacteriophage have been cloned on an approximately 7200-bp ClaI fragment and their sites relative to each other and to the colicin immunity (imm) gene have been mapped. The inhibition of wild-type T7 by the clone is shown to be caused by the same gene or genes (pic) that cause the inhibition of T7 kinase-negative mutants and is a different gene than the one that causes inhibition of T5 (ibf or abi). The pic gene does not hybridize to the pif genes of the F plasmid that also cause the replication of T7 to be inhibited. The abi gene and the pic gene map very closely together but are under the control of different promoters. The abi gene has a maximum size of 900 bp and lies approximately 3000 bp away from the immunity gene, distal to the colicin gene. A site which maps in or near the gene binds very tightly to Escherichia coli RNA polymerase. The pic gene or genes lie between the abi gene and the imm gene and are contiguous with abi. Promoters for pic have been mapped and hypotheses to explain the inhibition of T7 by a cloned gene but not the whole ColIb plasmid are presented.
抑制T5样和T7噬菌体复制的大肠杆菌素Ib（ColIb）质粒基因已被克隆到一个约7200碱基对的ClaI片段上，并且已绘制出它们彼此之间以及与大肠杆菌素免疫（imm）基因的相对位置。该克隆对野生型T7的抑制作用被证明是由导致对T7激酶阴性突变体产生抑制作用的相同基因或基因（pic）引起的，并且与导致对T5产生抑制作用的基因（ibf或abi）不同。pic基因与F质粒的pif基因不杂交，F质粒的pif基因也会导致T7的复制受到抑制。abi基因和pic基因紧密连锁在一起，但受不同启动子的控制。abi基因的最大大小为900碱基对，位于距离免疫基因约3000碱基对处，在大肠杆菌素基因的远端。一个定位在该基因内或附近的位点与大肠杆菌RNA聚合酶紧密结合。pic基因位于abi基因和imm基因之间，并且与abi相邻。已绘制出pic的启动子，并提出了一些假设来解释克隆基因而非整个ColIb质粒对T7的抑制作用。
