Buvinger W E, Riley M
J Bacteriol. 1985 Sep;163(3):858-62. doi: 10.1128/jb.163.3.858-862.1985.
The chromosomal DNA that lies between the lacI and lacZ genes of Klebsiella pneumoniae constitutes a 196-base pair intercistronic region that contains regulatory sequences for both genes. The probable locations of specific regulatory elements for both lacI and lacZ genes were determined by analogy with the corresponding Escherichia coli sequences. A recombinational event in ancestral DNA evidently has inverted the transcriptional direction of lacI in K. pneumoniae relative to the transcriptional direction of lacI in E. coli. One end of the inversion was located within a 19-base pair sequence in the K. pneumoniae regulatory region. Sequences partially homologous to these 19 base pairs were found in two locations on either side of the E. coli lacI gene. The nucleotide sequence of the lac regulatory region in K. pneumoniae exhibits more than one possibility for folded tertiary structures. The spatial relationships of transcriptional binding sites differ in two possible structures. Associations of regulatory and transcriptional proteins with the DNA might affect conformation of the regulatory sequences and, as a consequence, transcription of the lac genes.
肺炎克雷伯菌lacI和lacZ基因之间的染色体DNA构成了一个196个碱基对的顺反子间区域，其中包含这两个基因的调控序列。通过与相应的大肠杆菌序列类比，确定了lacI和lacZ基因特定调控元件的可能位置。祖先DNA中的一次重组事件显然使肺炎克雷伯菌中lacI的转录方向相对于大肠杆菌中lacI的转录方向发生了反转。反转的一端位于肺炎克雷伯菌调控区域的一个19个碱基对的序列内。在大肠杆菌lacI基因两侧的两个位置发现了与这19个碱基对部分同源的序列。肺炎克雷伯菌中lac调控区域的核苷酸序列展现出不止一种折叠三级结构的可能性。转录结合位点的空间关系在两种可能的结构中有所不同。调控蛋白和转录蛋白与DNA的结合可能会影响调控序列的构象，进而影响lac基因的转录。
