Knapp S, Then I, Wels W, Michel G, Tschäpe H, Hacker J, Goebel W
Mol Gen Genet. 1985;200(3):385-92. doi: 10.1007/BF00425721.
The haemolysin (hly) determinant of the plasmid pHly152 contains an IS2 element at 469 bp upstream of the hlyC gene. The sequence at the other (right-hand) end (RS) also shows multiple hybridization with the plasmid pHly152 and the chromosome of some Escherichia coli strains but the nucleotide sequence of this region does not reveal the typical properties of an IS element. Similar arrangements in the regions flanking the hly determinant are also found on various Hly plasmids from uropathogenic E. coli strains. Chromosomal hly determinants lack both flanking sequences (IS2 and RS) in the immediate vicinity of the hly genes. The sequences immediately upstream of the hlyC gene have been determined from several chromosomal hly determinants and compared with the corresponding sequence of the hly determinant of the plasmid pHly152. We show that these sequences, which contain one promoter (left promoter, phlyL) in all hly determinants tested, vary considerably although common sequence elements can still be identified. In contrast, only relatively few nucleotide exchanges have been detected in the adjacent structural hlyC genes. The A + T content of the 200 bp sequence upstream of hlyC is very high (72 mol% A + T) but even the structural hly genes show a considerably higher A + T content (about 60 mol%) than the E. coli chromosome on average (50 mol% A + T) suggesting that the hly determinant may not have originated in E. coli.
质粒pHly152的溶血素（hly）决定簇在hlyC基因上游469 bp处含有一个IS2元件。另一端（右侧）序列（RS）也与质粒pHly152和一些大肠杆菌菌株的染色体呈现多重杂交，但该区域的核苷酸序列并未显示出IS元件的典型特征。在来自尿路致病性大肠杆菌菌株的各种Hly质粒上，也发现了hly决定簇侧翼区域的类似排列。染色体hly决定簇在hly基因紧邻区域缺乏两侧的序列（IS2和RS）。已从多个染色体hly决定簇测定了hlyC基因紧邻上游的序列，并与质粒pHly152的hly决定簇的相应序列进行了比较。我们发现，这些序列在所有测试的hly决定簇中都含有一个启动子（左侧启动子，phlyL），尽管仍可识别出共同的序列元件，但它们差异很大。相比之下，在相邻的结构hlyC基因中仅检测到相对较少的核苷酸交换。hlyC上游200 bp序列的A+T含量非常高（72 mol% A+T），但即使是结构hly基因的A+T含量（约60 mol%）也明显高于大肠杆菌染色体的平均水平（50 mol% A+T），这表明hly决定簇可能并非起源于大肠杆菌。
