Boor K J, Duncan M L, Price C W
Department of Food Science and Technology, University of California, Davis 95616, USA.
J Biol Chem. 1995 Sep 1;270(35):20329-36. doi: 10.1074/jbc.270.35.20329.
The gene encoding the beta subunit of Bacillus subtilis RNA polymerase was isolated from a lambda gt11 expression library using an antibody probe. Gene identity was confirmed by the similarity of its predicted product to the Escherichia coli beta subunit and by mapping an alteration conferring rifampicin resistance within the conserved rif coding region. Including the rif region, four colinear blocks of sequence similarity were shared between the B. subtilis and E. coli beta subunits. In E. coli, these conserved blocks are separated by three regions that either were not conserved or were entirely absent from the B. subtilis protein. The B. subtilis beta gene was part of a cluster with the order rplL (encoding ribosomal protein L7/L12), orf23 (encoding a 22,513-dalton protein that is apparently essential for growth), rpoB (beta), and rpoC (beta'). This organization differs from the corresponding region in E. coli by the inclusion of orf23. Experiments using promoter probe vectors and site-directed mutagenesis located a major rpoB promoter overlapping the 3'-coding region of orf23, 250 nucleotides upstream from the beta initiation codon. Thus, the B. subtilis rpoB region differs from its E. coli counterpart in both genetic and transcriptional organization.
利用抗体探针从λgt11表达文库中分离出编码枯草芽孢杆菌RNA聚合酶β亚基的基因。通过其预测产物与大肠杆菌β亚基的相似性以及在保守的利福平编码区域内定位赋予利福平抗性的突变，证实了基因的同一性。包括利福平区域在内，枯草芽孢杆菌和大肠杆菌的β亚基共有四个共线的序列相似性区域。在大肠杆菌中，这些保守区域被三个在枯草芽孢杆菌蛋白质中不保守或完全不存在的区域隔开。枯草芽孢杆菌的β基因是一个基因簇的一部分，该基因簇的顺序为rplL（编码核糖体蛋白L7/L12）、orf23（编码一种显然对生长至关重要的22513道尔顿蛋白质）、rpoB（β）和rpoC（β'）。这种组织方式与大肠杆菌中的相应区域不同，因为包含了orf23。使用启动子探针载体和定点诱变的实验确定了一个主要的rpoB启动子，它与orf23的3'编码区域重叠，位于β起始密码子上游250个核苷酸处。因此，枯草芽孢杆菌的rpoB区域在遗传和转录组织上与其大肠杆菌对应区域不同。
