Buvinger W E, Riley M
J Bacteriol. 1985 Sep;163(3):850-7. doi: 10.1128/jb.163.3.850-857.1985.
The nucleotide sequences of the Klebsiella pneumoniae lacI and lacZ genes and part of the lacY gene were determined, and these genes were located and oriented relative to one another. The K. pneumoniae lac operon is divergent in that the lacI and lacZ genes are oriented head to head, and complementary strands are transcribed. Besides base substitutions, the lacZ genes of K. pneumoniae and Escherichia coli have suffered short distance shifts of reading frame caused by additions or deletions or both during evolutionary divergence from a common ancestral gene. Relative to corresponding E. coli sequences, the nucleotide sequences of the lacZ and lacY genes are 61 and 67% conserved, and the lacI genes are 49% conserved. A comparison of both nucleotide and amino acid sequences revealed that the K. pneumoniae and E. coli lacI genes and lac repressor proteins each are related to the galR gene and gal repressor of E. coli to about the same extent. In terms of evolutionary relationships, the divergence of the forerunner of the galR gene from an ancestral lac repressor gene preceded separation and differentiation of the K. pneumoniae and E. coli lac repressor genes.
测定了肺炎克雷伯菌lacI和lacZ基因以及部分lacY基因的核苷酸序列，并确定了这些基因的位置及其相互间的方向。肺炎克雷伯菌的乳糖操纵子是发散型的，即lacI和lacZ基因头对头排列，互补链被转录。除碱基替换外，肺炎克雷伯菌和大肠杆菌的lacZ基因在从共同祖先基因进化分歧过程中因插入、缺失或两者兼而有之而发生了短距离的读框移位。相对于相应的大肠杆菌序列，lacZ和lacY基因的核苷酸序列保守性分别为61%和67%，lacI基因的保守性为49%。核苷酸序列和氨基酸序列的比较均显示，肺炎克雷伯菌和大肠杆菌的lacI基因及乳糖阻遏蛋白与大肠杆菌的galR基因及半乳糖阻遏蛋白的亲缘关系大致相同。就进化关系而言，galR基因的前身从祖先乳糖阻遏基因的分歧发生在肺炎克雷伯菌和大肠杆菌乳糖阻遏基因的分离和分化之前。
